Patch adds a LuaJIT fuzzer based on libprotobuf-mutator and LibFuzzer.
Grammar is described via messages in protobuf format, serializer is
applied to convert .proto format to string.

For displaying generated code on the screen during fuzzing set
the environment variable 'LPM_DUMP_NATIVE_INPUT'.

For displaying error messages from lua functions set
the environment variable 'LUA_FUZZER_VERBOSE'.

Note: UndefinedBehaviourSanitizer is unsupported by LuaJIT (see #8473),
so fuzzing test is disabled when CMake option ENABLE_UB_SANITIZER is
passed.

Closes #4823

NO_DOC=<fuzzing testing of LuaJIT>
NO_TEST=<fuzzing testing of LuaJIT>

(cherry picked from commit a287c853)

Added Google's 'libprotobuf-mutator' and 'protobuf' libraries
for developing grammar-based LuaJIT and SQL fuzzers based on
LibFuzzer.

It is needed to build protobuf module from source because
by default, the system-installed version of protobuf is used
by libprotobuf-mutator, and this version can be too old.

Part of #4823

NO_CHANGELOG=<dependencies>
NO_DOC=<dependencies>
NO_TEST=<dependencies>

(cherry picked from commit b11072a6)

Added options for fuzzing and for getting more information
on debugging.

NO_CHANGELOG=<fuzzing options>
NO_DOC=<fuzzing options>
NO_TEST=<fuzzing options>

(cherry picked from commit 69f21e25)

To achieve that, we bypass the read-only check for the _truncate system
space in box_process1() and perform it in the on_replace system trigger
instead, when we know which space is truncated.

Note, we have to move the check for insertion of a new record into the
_truncate system space before the read-only check in the on_replace
trigger callback; this is needed for initial recovery with a non-empty
_truncate space to work. While we are at it, let's use recovery_state to
make the check explicit.

Closes #5616

@TarantoolBot document
Title: Mention that temp and local spaces can be truncated in ro mode

DML operations on temporary and local spaces can be performed even if
the instance is in the read-only mode, but DDL operations (such as
`alter`) are forbidden in this case[^1]. Technically, `truncate` is
a DDL operation so initially it was forbidden as well. However, it
should be safe to perform this operation on a temporary or local space
because logically it only modifies the data stored in the space (like
DML) and it isn't replicated (see tarantool/tarantool#4263). So starting
from Tarantool 2.11.1 we allow users to truncate temporary spaces in the
read-only mode.

[^1]: https://www.tarantool.io/en/doc/latest/concepts/replication/repl_architecture/#replication-local

(cherry picked from commit 054526ac)

A read source iterator stores statements in a vy_history object using
vy_history_append_stmt(). If a statement can be referenced, it's
reference counter is incremented. If it can't, i.e. it belongs to a
memory source, it's stored in a vy_history object without referencing.

This works fine because memory sources are append-only. A problem arises
only when we get to scanning disk sources. Since we yield while reading
disk, a dump task may complete concurrently dropping the memory sources
and possibly invalidating statements stored in the iterator history.
Although we drop the history accumulated so far and restart the
iteration from scratch in this case, there's still an issue that can
result in a use-after-free bug in vy_read_iterator_next().

The problem is that we access the current candidate for the next
statement while evaluating a disk source after a disk read. If 'next'
refers to a referenced statement, it's fine, but if it refers to a
statement from a memory source, it may cause use-after-free because
the memory source may be dropped during a disk read.

To fix this issue, let's make vy_history_append_stmt() copy statements
coming from memory sources. This should be fine performance-wise because
we copied memory statements eventually in vy_history_apply() anyway,
before returning them to the user.

Note that we also have to update vy_read_iterator_restore_mem() because
it implicitly relied on the fact that 'next' coming from a memory source
can't be freed by vy_mem_iterator_restore(), which cleans up the memory
source history. Now, it isn't true anymore so we have to temporarily
take a reference to 'next' explicitly.

Closes #8852

NO_DOC=bug fix
NO_TEST=tested by ASAN

(cherry picked from commit 0e5a3cc2)

In scope of the commit 82f4b4a3 ("lib/core/fiber: Increase default
stack size") the default value of fiber stack size is increased up to
512 Kb (you can find the reasons in the aforementioned commit message
and in https://github.com/tarantool/tarantool/issues/3418 description).

Some of the tests in test/PUC-Rio-Lua-5.1-test suite in LuaJIT repo
(e.g. some cases with deep recursion in errors.lua or pm.lua) have
already been tweaked according to the limitations mentioned in
https://github.com/tarantool/tarantool/issues/5782, but the crashes
still occurs while running LuaJIT tests with ASan support enabled.

To make the testing routine more convenient, FIBER_STACK_SIZE option is
introduced to Tarantool CMake machinery. One can provide the size either
by raw digits (i.e. in bytes) or using Kb/Mb suffixes for convenience.

A couple of important nits:
* If the given value is not a multiple of 4Kb, CMake machinery adjusts
  it up to the nearest one greater than this value.
* If the adjusted value is less than 512Kb, configuration fails with the
  corresponding CMake fatal error.

Follows up #3418
Relates to #5782

@TarantoolBot document
Title: introduce FIBER_STACK_SIZE configuration option

To make managing of the default fiber stack size more convenient, the
corresponding CMake option is added.

**NB**: The stack size can't be less than 512Kb and if the given value
is not a multiple of 4Kb, CMake machinery adjusts it up to the nearest
one greater than this value.

(cherry picked from commit ff57f990)

In the original commit 5f6d367c ("compat: add is_new and
is_old to options") `compat.<option_name>:is_new()` and `:is_old()`
were introduced, but by mistake they contained different usage
messages. This patch updates `:is_new()` usage msg to more
informative one from `:is_old()`.

Follows up #8807

NO_CHANGELOG=changelog from 5f6d367c is valid
NO_DOC=doc from 5f6d367c is valid

(cherry picked from commit f590ec22)

It used to be somewhat complicated to check the effective value
of a compat option, because `<option_name>.current` could contain
'default' state.
This patch introduces helper functions that take care of that.

The following alternatives were considered:
* `compat.<option_name>.effective` - it is excessive in the presence
  if `current` and `default`, and is visible in serialization
* `compat.<option_name>.get()` - while it is a function, it does only
  half of the work required, user still has to compare result to 'new'

Closes #8807

@TarantoolBot document
Title: Add `:is_new/old()` helpers to tarantool.compat options

`compat.<option_name>.current` can be 'new', 'old' or 'default',
thus when it is default there must be an additional check if
`compat.<option_name>.default` is 'new'. It is handier to have a
helper to deal with that instead of complicated `if`:
* check if effective value is 'new' before the patch:
  ```lua
  if compat.<option_name>.current == 'new' or
          (compat.<option_name>.current == 'default' and
           compat.<option_name>.default == 'new') then
      ...
  end
  ```
* after the patch:
  ```lua
  if compat.<option_name>:is_new() then
      ...
  end
  ```

Please update [tutorial on using compat], maybe add an example to
[Listing options details].

[tutorial on using compat]: https://www.tarantool.io/en/doc/latest/reference/reference_lua/compat/compat_tutorial/
[Listing options details]: https://www.tarantool.io/en/doc/latest/reference/reference_lua/compat/compat_tutorial/#listing-options-details

(cherry picked from commit 5f6d367c)

1. Make double-formatted fields accept integer and float values.
2. Make indexes compare the values as double if the field key type
   is FIELD_TYPE_DOUBLE.
3. Make hashers cast double key field to double before hashing, so
   we are able to insert and select any int, uint, float or double
   if their value casted to double is equal (for double keys).

Notes about tuple_compare.cc:

Since now `mp_compare_double` casts any value placed in field to
double it was renamed to `mp_compare_as_double` to not semantically
conflict with existing `mp_compare_double_*` functions.

Notes about tuple_hash.cc:

The hashee cast result is encoded in MP_DOUBLE and hashed for
backward compatibility reasons.

Since now the field hashing function (tuple_hash_field) requires
field type to hash the field correctly, a new parameter has been
introduced.

By the way added assertions to the generic `field_hash` to prevent
invalid hashing for new precompiled hashers and made
`key_hash_slowpath` static cause it's only used in this file.

Closes #7483
Closes #5933
Unblocks tarantool/crud#298

@TarantoolBot document
Title: It's not required to ffi-cast integral floating point to
double anymore.

The page describing tarantool data model states that:

> In Lua, fields of the double type can only contain non-integer
> numeric values...

If the patch is merged this isn't the case anymore, so this
statement and the code snippet below it should be updated.

Link to the document: [Data storage](https://www.tarantool.io/en/doc/latest/concepts/data_model/value_store/#field-type-details).

Affected segments:

> double. The double field type exists mainly to be equivalent
> to Tarantool/SQL’s DOUBLE data type. In msgpuck.h (Tarantool’s
> interface to MsgPack), the storage type is MP_DOUBLE and the
> size of the encoded value is always 9 bytes. In Lua, fields of
> the double type can only contain non-integer numeric values and
> cdata values with double floating-point numbers. Examples: 1.234,
> -44, 1.447e+44.
>
> To avoid using the wrong kind of values inadvertently, use
> ffi.cast() when searching or changing double fields. For example,
> instead of space_object:insert{value} use ffi = require('ffi')
> ... space_object:insert({ffi.cast('double',value)}). Example:
>
> ```
> s = box.schema.space.create('s', {format = {{'d', 'double'}}})
> s:create_index('ii')
> s:insert({1.1})
> ffi = require('ffi')
> s:insert({ffi.cast('double', 1)})
> s:insert({ffi.cast('double', tonumber('123'))})
> s:select(1.1)
> s:select({ffi.cast('double', 1)})
> ```

(cherry picked from commit 51af059c)

This update pulls the following commits:
* Add mp_read_double_lossy without direct convertibility checks
* Fix mp_read_double_lossy tests freebsd build

These commits introduce a function required to compare and hash
msgpack values of double key fields as double.

Need for #7483, #5933

NO_DOC=see the next commit
NO_CHANGELOG=see the next commit

(cherry picked from commit be47f8fb)

Test uses a popen module that starts tarantool process in background
mode. Tarantool process started in background mode forks a new process
and closes a parent, after that popen loses a PID of the started process
and `ph:kill()` and `ph:terminate()` doesn't work anymore. It leads to
non-terminated tarantool processes after running the test.

Patch fixes that by running `kill` using os.execute with a PID of
tarantool process written to a pid file.

Follows up #6128

NO_CHANGELOG=fix test
NO_DOC=fix test

(cherry picked from commit 88686227)

Fixed the implementation of the box console.
Before this fix, result of `\set language` is shared between clients
via `console.connect`, despite the fact that clients have different
`box.session.id`. Now the parameter of the selected language is stored
by each client in his own `box.session.storage`.

Fixes #8817

NO_DOC=bugfix

(cherry picked from commit e4fda4b7)

* test: fix flaky <unit-jit-parse.test.lua>
* Fix use-def analysis for vararg functions.
* Fix use-def analysis for BC_VARG.
* Fix TNEW load forwarding with instable types.
* Fix memory probing allocator to check for valid end address, too.
* Another fix for lua_yield() from C hook.
* Fix lua_yield() from C hook.
* Fix saved bytecode encapsulated in ELF objects.
* x64: Fix 64 bit shift code generation.
* Fix canonicalization of +-0.0 keys for IR_NEWREF.
* test: add utility for parsing `jit.dump`
* test: split utils.lua into several modules
* test: rewrite lj-49-bad-lightuserdata test in C
* test: rewrite misclib-sysprof-capi test in C
* test: rewrite misclib-getmetrics-capi test in C
* test: introduce utils.h helper for C tests
* test: introduce module for C tests
* test: fix setting of {DY}LD_LIBRARY_PATH variables
* build: fix build with LUAJIT_USE_GDBJIT enabled
* ci: update the branch name for Tarantool 2.11

Closes #8718
Part of #7900
Part of #8516

NO_DOC=LuaJIT submodule bump
NO_TEST=LuaJIT submodule bump

Previous attempt to fix flakiness in commit 6a2c73f8 ("test: fix
flakiness in gh_6128_background_mode_test") used a constant buffer size
in check_err_msg function. Tarantool 2.10 has a bit bigger log before a
desired message that other versions of Tarantool and it leads to a this
resulted in a truncated message ("entering the even" instead of
"entering the event loop"). Patch replaces check_err_msg()
implementation to grep_log used in luatest, it reads the whole log.

Also patch renames check_err_msg to check_msg, because "entering the
event loop" is not an error message.

Follows up #6128

NO_CHANGELOG=fix test
NO_DOC=fix test

(cherry picked from commit 1c8e7124)

Function execution permissions should only be checked on constraint
creation.

So when the function is used to check a tuple access rights don't
have to be checked on each call for the current user.

Closes #7873

NO_DOC=bugfix

(cherry picked from commit 6b8f2c5f)

Function execution permissions should only be checked on functional
index creation and on functional index function set.

So when the function is used by key_list_iterator its rights don't
have to be checked on each call for the current user.

Part of #7873

NO_DOC=bugfix
NO_CHANGELOG=see the next commit

(cherry picked from commit ddbdb77a)

When a space is altered, we abort all in-progress transactions and delete
all stories related to that space: the problem is we don't delete the
stories' read gaps, which are also linked to the stories' transactions,
which get cleaned up on transaction destruction — this, in turn, results in
heap-use-after-free. To fix this, clean up stories' read gap in
`memtx_on_space_delete` — we don't do this in `memtx_tx_story_delete` since
it expects the story to not have any read gaps (see
`memtx_tx_story_gc_step`).

Tested this patch manually against Nick Shirokovskiy's experimental
small-ASAN integration branch.

Closes #8781

NO_DOC=bugfix
NO_TEST=<already covered by existing tests, but was not detectable by ASAN>

(cherry picked from commit e1ed31bb)

Test runs an external process with tarantool that writes to a log file.
Then test reads that log file and searches a string with required
message in it (see function check_err_msg). Test was flaky on macOS and
I suspect it was happening due to a high log level - timeout was not
enough to wait message in the log file.

Patch decreases a log level to a default value and replaces io
functions with the similar alternatives in a fio module. Using
fio functions allows to not block fibers.

NO_CHANGELOG=test fix
NO_DOC=test fix

(cherry picked from commit 47380bb7)

The xlog reader Lua module uses the xlog_cursor_next_row, which decodes
the row header with xrow_header_decode. The latter silently ignores any
unknown fields, which complicates catching bugs when garbage is written
to a row header by mistake, for example, see #8783.

Let's parse a row header without using xrow_header_decode in the xlog
reader module, like we parse a row body, and output all unknown/invalid
keys as is.

To do that, we have to extend the xlog cursor API with the new method
xlog_cursor_next_row_raw that returns a pointer to the position in the
tx buffer where the next xrow is stored without advancing it. To avoid
a memory leak in case the caller fails to parse an xrow returned by this
function, we also have to move the call to xlog_tx_cursor_destroy from
xlog_tx_cursor_next_row to xlog_cursor_next_tx.

While we are at it,
 - Don't raise an error if a key type encountered in a row body is
   invalid (not an integer). Instead, silently ignore such keys.
 - Remove the useless body MsgPack validness check because we already
   check it after decoding the header.
 - Add error injection based tests to check all the corner cases.

NO_DOC=bug fix

(cherry picked from commit 8a25d170)

To avoid garbage written to xlog.

Closes #8783

NO_DOC=bug fix
NO_TEST=next commit

(cherry picked from commit f058cee7)

Apple's libunwind for AArch64 returns the Instruction Pointer with the
Pointer Authentication Codes (bits 47-63) even though Tarantool is compiled
for arm64 (not arm64e) architecture, so we have to strip them out [1].
Although there is the ptrauth_strip macro for this purpose, it works only
if compilation target is arm64e (not arm64) [2].

1. https://developer.apple.com/documentation/security/preparing_your_app_to_work_with_pointer_authentication#3042105
2. https://github.com/dotnet/runtime/issues/42955#issuecomment-886910180

Closes #8074
Closes tarantool/tarantool-qa#308
Closes tarantool/tarantool-qa#309

NO_DOC=bugfix

(cherry picked from commit 88990e2f)

<luaT_pushtuple> function created a new GCfunc object for a tuple __gc
handler (i.e. <lbox_tuple_gc>), having no upvalues, on each call when
tuple object for Lua world is created.

The change introduces the reference to the single GCfunc object created
on Tarantool startup and stored to Lua registry. Using this approach in
scope of <luaT_pushtuple> is aimed to reduce Lua GC memory usage.

Part of #5201

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

Reviewed-by: Vladimir Davydov <vdavydov@tarantool.org>
Reviewed-by: Sergey Kaplun <skaplun@tarantool.org>
Signed-off-by: Igor Munkin <imun@tarantool.org>
(cherry picked from commit 8d7d1460)

Space index build and space format checking operations don't destroy space
iterator on `txn_check_singlestatement` failure — fix this.

Closes #8773

NO_DOC=bugfix
NO_TEST=<leak happens in small, cannot be detected by sanitizer>

(cherry picked from commit 6689f511)

The procedure name cache uses a region for hash table entry allocation, but
the cache is a thread local variable, while the `region` uses a `slab`
allocator the lifetime of which is bounded by `main`, while thread locals
are destroyed after `main`: use the `malloc` allocator instead.

Benchmark from #7207 shows that this change does not effect performance.

Closes #8777

NO_CHANGELOG=<leak does not affect users>
NO_DOC=bugfix
NO_TEST=<detected by ASAN>

(cherry picked from commit 7135910e)

Before a commit ec1af129 ("box: do not close xlog file descriptors in
the atfork handler") there was a bug when Tarantool with enabled
background mode via environment variable could lead a crash:

NO_WRAP
```
$ TT_PID_FILE=tarantool.pid TT_LOG=tarantool.log TT_BACKGROUND=true TT_LISTEN=3301 tarantool -e 'box.cfg{}'
$ tail -3 tarantool.log
2021-11-02 16:05:43.672 [2341202] main init.c:696 E> LuajitError: cannot read stdin: Resource temporarily unavailable
2021-11-02 16:05:43.672 [2341202] main F> fatal error, exiting the event loop
2021-11-02 16:05:43.672 [2341202] main F> fatal error, exiting the event loop
```
NO_WRAP

With commit ec1af129 ("box: do not close xlog file descriptors in
the atfork handler") described bug could not be reproduced.

Proposed patch adds a test that starts Tarantool in background mode
enabled via box.cfg option and via environment variable TT_BACKGROUND to
make sure this behaviour will not be broken in a future.

Closes #6128

NO_DOC=test

(cherry picked from commit f676fb7c)

There are sporadic segfaults in libunwind during backtrace_collect().
Reproducible with the latest version, and there are open issues with
similar stacks:

https://github.com/libunwind/libunwind/issues/150
https://github.com/libunwind/libunwind/issues/260
https://github.com/libunwind/libunwind/issues/473

Let's disable ENABLE_BACKTRACE for AArch64 Linux until these issues are
resolved in libunwind.

Closes #8572
Part of #8791

NO_DOC=bugfix

(cherry picked from commit 418e749c)

The ability to support backtraces is checked in cmake/compiler.cmake,
it makes no sense to duplicate the check in rpm/tarantool.spec. Also do
not enable backtraces unconditionally in apk/APKBUILD and static-build.

Part of #6998

NO_DOC=build
NO_TEST=build
NO_CHANGELOG=build

(cherry picked from commit f7c4a34a)

There's case when a transaction is rolled back from prepared
state. This happens when WAL fails, synchronized replication
confirmation failure or perhaps in other similar cases. By design
other RW transactions and transactions with READ_COMMITTED
isolation level are allowed to read prepared state. All these
transactions must be aborted in case of rollback of prepared
transaction since they definitely have read no more possible
database state.

This patch implements this abortion.

Closed #8654

NO_DOC=bugfix

(cherry picked from commit 54986902)

Rollback is rather complicated part if MVCC implementation that
is meant to handle two kinds of rollback:
* rollback from in-progress state, if box.rollback() is called.
* rollback from prepared state, when WAL fails.
Unfortunately the last one was not properly tested and surely
has at least one flaw. When an inserting transaction becomes
prepared its stories could be linked as deleted (via del_stmt
pointer) by other in-progress transactions in order to maintain
correct visibility. The problem is that in case of rollback of
such prepared transaction those links remained. Broken links
breaks the chain structure, and some older changes (that were
linked as deleted before that hapless preparation) can become
visible to other transaction.

Refactor, simplify a bit that part of code and fix the issue
described above; cover with tests.

Closes #8648

NO_DOC=bugfix

(cherry picked from commit 85569d9c)

Almost completely rewrite, simplify and comment this part of code.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit e9015074)

Almost completely rewrite, simplify and comment this part of code.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit 63da3bed)

The latter flag is a bit wider: it reveals not only inserting
statements after deleting by the same transaction, but also
replacing and deleting statements after all kinds of previois
changes but the same transaction. This extended behavior will
be used in further commits.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit 3cfa6756)

It was an ugly solution when MVCC engine requires outside engine
to set this flag which is not convenient.

Remove it and use mode arguments to set up proper read trackers.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit 74149734)

The function memtx_tx_story_delete is expected to delete fully
unlinked stories and thus should not try to unlink something by
itself. So remove unlink and add asserts instead.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit 07067407)

Now there are three kinds of very close trackers:
* The transaction have read some tuple that is not committed and
  thus not visible. This kind is now stored as gap_item with
  is_nearby = false.
* The transaction made a select or range scan, reading a key or
  range between two adjacent tuples of the index. This kind is
  stored as gap_iteam with is_nearby = true.
* A transaction completed a full scan of unordered index. This
  kind is stored as full_scan_item.

All these trackers serve for the same thing: to record a fact
that a transaction read something but didn't see anything.

There are some problems with the current solution:
* gap_item with is_nearby = false has several unused members that
  just consume space.
* bool is_nearby flag for type descriptin is an ugly solution.
* full_scan_item is separated from logically close items.

This commit joins all these trackers under one base (that is
struct gap_item_base) and solves problems above.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit f8d97a2e)

Now read trackers are used both for cases when a transaction has
read an existing value and it has read nothing (read by key but
there was no visible tuple in this place). For latter case an
additional index_mask was used to identify from which index the
read was done. Along with that there was per-index interval gap
trackers.

This patch divides area of responsibility between read trackers
and gap tracker in the following way:
* Reads of existing visible values are stored in read trackers.
* Reads of non-existing or non-visible values are store in gap
  trackers.

This new approach allows to provide new invariants: gap trackers
are stored only at top of chain, and read trackers are stored
only at topmost committed story in chain.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit 7b8b78be)

In further commit this list will be used for tracking all read
gaps, not only 'nearby'. Since this rename has rather huge
diff, let's make it in separate commit.

No logical changes.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit d3feb691)

In our SQL implementation temporary spaces are used. They come to
MVCC engine in two variants - NULL or ephemeral. In both cases
MVCC engine must not do anything, there are several checks for
that in different parts of code.

Normalize these checks and make them similar to each other.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit 86a8155c)

The only place where this static function is used is more general
static function - memtx_tx_track_read_story. This is a bit
confusing - usually slow variant stand for public inline 'fast'
method.

So merge both functions in one.

Part of #8648
Part of #8654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

(cherry picked from commit 32e41b7a)

By a mistake in 8a565144 a shortcut was added to procedure
that handles gap write: it was considered that if the writing
transaction is the same as reading - there is no actual conflict
that must be stored further. That was a wrong decision: if such
a transaction yields and another transaction comes and commits
a value with the same key - the first one must go to conflicted
state since it has read no more possible state.

Another similar mistake was made in e6f5090c, where writing
after full scan of the same transaction was not tracked as read.
Obviously that was wrong: if some other transaction overwrites
the key and commits - this transaction must go to read view since
it did not see anything by this key which is not so anymore.

Fix it, reverting the first commit and an modifying the second and
add a test.

Closes #8326

NO_DOC=bugfix

(cherry picked from commit b41c4546)