Support Pre-Vote in Raft: when a node knows, that some of the peers see
the leader of the current term, it doesn't start elections. Even when it
doesn't have a connection to the leader.

Don't use the machinery yet: nodes never share info on whether they see
the leader.

Part-of #6654

NO_DOC=no user-visible changes
NO_CHANGELOG=no user-visible changes

Our checkpatch.pl script demands that every new function has a comment.
One new function will be added to raft_ev.h in the following commits,
and, according to the new rules, it has to have a comment.

Having one function in a file commented looks stupid, so let's add
comments to every such function in raft_ev.h

NO_DOC=making lint happy
NO_CHANGELOG=making lint happy
NO_TEST=making lint happy

raft_checkpoint_remote and raft_worker_handle_broadcast perform the same
job of filling the raft message with a complete raft state.

Let's fix that.

Part-of #6654

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

Start counting replicas, whose connections are "healthy", e.g. there are
both relay and applier in SUBSCRIBE state.

Introduce triggers for the events of "healthy quorum" loss and gain.
"healthy quorum" is the same as replication_synchro_quorum.

The triggers will be used in raft pre-vote and synchro queue owner
fencing. Both these features require tracking whether there is a quorum
of nodes reachable from the local node.

Pre-requisite #6654
Pre-requisite #6661

NO_DOC=no user-visible changes
NO_CHANGELOG=no user-visible changes
NO_TEST=preparatory patch

MVCC must track a read set of transaction, including cases when
the select returns an empty result. In this case MVCC has two
options: to store a point key if the select has a full key or
to store a gap otherwise.

By a mistake the second variant was not implemented. Fix it now.

Closes #7025

NO_DOC=bugfix

To implement online space upgrade, we need to add stub calls to the
following code paths and data structures:

 - struct space: add a pointer to space upgrade state.
 - struct space_opts: add a pointer to space upgrade definition.
 - CheckSpaceFormat::prepare: skip space check if the format is changed
   in the scope of space upgrade.
 - alter_space_do: check space upgrade state and fail alter if upgrade
   is in progress.
 - alter_space_commit: run background worker for space upgrade.
 - space_on_final_recovery_complete: restart upgrade after recovery.
 - result_processor: apply space upgrade transformations to tuples
   returned to the user by box functions.

We also need to:
 - Add a new error code ER_WRONG_SPACE_UPGRADE_OPTIONS, which we will
   use on error decoding upgrade options, stored in space options.
 - Load space upgrade Lua modules. The modules are supposed to define
   box.internal.space.upgrade method, which if available is used by
   box.schema.space.upgrade.
 - Add check_param, check_param_table and normalize_format helpers to
   box.internal, because we will use them from space.upgrade Lua code.

Note, the space upgrade state will be reference counted, because
background space upgrade may complete while some fiber is reading
from the upgraded space (there may be yields in Vinyl). For this fiber
to process the result correctly, it has to increment the reference
counter of the space upgrade state before reading from the space.

NO_DOC=ee
NO_TEST=ee
NO_CHANGELOG=ee

A convenient helper that is supposed to apply various transformations
to a tuple fetched from a space before returning it to the user.
Usage:

  struct result_processor res_proc;
  result_process_prepare(&res_proc, space);
  rc = index_get(index, key, part_count, result);
  result_process(&res_proc, &rc, result);

We need to split the procedure into two parts, because index_get and
similar methods may yield in case of Vinyl. The 'prepare' method is
supposed to pin all data structures needed to process the result in the
result_processor struct while the 'process' method is supposed to
release them.

Currently, the new methods do absolutely nothing. They will be used to
convert tuples during space upgrade.

NO_DOC=internal
NO_TEST=internal
NO_CHANGELOG=internal

The new helper function returns the space the iterator was created for.
It looks up the space by id and caches it in iterator struct. We need it
for space upgrade: we will use it in box_iterator_next() to update
tuples returned by iterator_next().

NO_DOC=internal
NO_TEST=internal
NO_CHANGELOG=internal

NO_DOC=code cleanup
NO_TEST=code cleanup
NO_CHANGELOG=code cleanup

It's a more appropriate name, because the function doesn't update
a space format - it just adjusts a format table to a normal form.

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

After this patch, it will be possible to perform permitted arithmetic
operations on DATETIME and INTERVAL values.

Closes #6773

@TarantoolBot document
Title: Field type interval is available in SQL

The INTERVAL field type is now available in SQL. INTERVAL values cannot
be compared. INTERVAL values can be explicitly and implicitly cast to
ANY. There are currently no literals for the INTERVAL field type.

Prior to this patch, the right operand was checked before the left. This
can lead to some complications when arithmetic operations are added for
the DATETIME and INTERVAL values. To avoid this, let's check the left
operand before the right one. This will cause the description of the
error to change, but nothing else.

Needed for #6773

NO_DOC=Not documented feature.

Part of #6773

NO_DOC=Will be added later.
NO_CHANGELOG=Will be added later.

This patch introduces basic INTERVAL support in SQL. After this patch,
it will be allowed to select INTERVAL values from spaces, insert them
into spaces, and use them in functions. CAST() from INTERVAL to STRING
and ANY is also supported.

Part of #6773

NO_DOC=Will be added later.
NO_CHANGELOG=Will be added later.

This patch fixes the error description for comparison in case the left
operand is comparable but the right operand is not.

Part of #6668
Needed for #6668

NO_DOC=Will be added in another commit.
NO_CHANGELOG=Will be added in another commit.

After this patch, using MAP and ARRAY in GROUP BY will throw an error
instead of an assertion.

Part of #6668
Needed for #6773

NO_DOC=Will be added in another commit.
NO_CHANGELOG=Will be added in another commit.

After this patch, when DISTINCT is used with MAP or ARRAY, an error will
be thrown instead of a segmentation fault.

Part of #6668
Needed for #6773

NO_DOC=Will be added in another commit.
NO_CHANGELOG=Will be added in another commit.

LuaJIT submodule is bumped to introduce the following changes:
* memprof: enrich symtab with newly loaded symbols
* memprof: extend symtab with C symbols

Within this changeset the new Lua module providing minimalistic AVL tree
implementation required for processing C symbols is introduced:
* utils/avl.lua: minimalistic AVL tree implementation

Closes #5813

NO_DOC=LuaJIT submodule bump
NO_TEST=LuaJIT submodule bump

Signed-off-by: Igor Munkin <imun@tarantool.org>

New field type INTERVAL is now supported by BOX.

Part of #6773

NO_DOC=INTERVAL has already been introduced earlier.

Part of #6773

NO_DOC=INTERVAL has already been introduced earlier.
NO_CHANGELOG=It will be added in another commit.

Part of #6773

NO_DOC=INTERVAL has already been introduced earlier.
NO_CHANGELOG=It will be added in another commit.

Part of #6773

NO_CHANGELOG=It will be added in another commit.

@TarantoolBot document
Title: New MsgPack extension type MP_INTERVAL

MsgPack extension type MP_INTERVAL was created to serialize values of
struct interval.

Description of serialized value:

------------------------------------------------------------
|MP_EXT|Size of packed interval|MP_INTERVAL|packed interval|
------------------------------------------------------------

Packed interval - packed number of non-zero fields and packed non-null
fields. Each packed field consists of two packed integer values - the
field ID and its value. The number of non-null fields can be zero, in
which case `packed interval` will be just packed integer `0`.

List of IDs:
0 - `year`
1 - `month`
2 - `week`
3 - `day`
4 - `hour`
5 - `minute`
6 - `second`
7 - `nanosecond`
8 - `adjust`

Example of packed interval value:

|C7|09|06|03|00|01|01|CCC8|03|D0B3|

Where
C7 - MP_EXT;
09 - size of packed interval value, 9 bytes;
06 - MP_INTERVAL;
03 - number of non-zero fields;
00 - ID of field `year`;
01 - packed value `1`;
01 - ID of field `month`;
CCC8 - packed value `200`;
03 - ID of field `day`;
D0B3 - packed value `-77`.

From there we can see, that the packed interval is actually
`1 year, 200 months and -77 days`.

This method is necessary to compare two INTERVAL values in Luatest.

Part of #6773

NO_DOC=Internal function.
NO_CHANGELOG=INTERVAL has already been introduced earlier.

Half of allocation functions in space_def_dup and space_def_new already
use xmalloc. Use xmalloc for the rest of allocations.

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

To implement space upgrade, we need a function that duplicates field_def
array, because we will store a new space format in space options.

To factor out field_def_array_dup from space_def_dup, let's allocate it
with a separate malloc rather than after space_def struct.

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

NO_DOC=internal
NO_CHANGELOG=internal

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

The function isn't used since commit 3dcc3fd6 ("Move
default_value_expr from field_def to tuple_field").

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

We have found that 301-basic.t from Lua harness tests became
flaky on macosx runners.
Please see https://github.com/tarantool/tarantool/issues/7058

 for
more details. Use simple workaround `collectgarbage('collect')`
for temporary workaround of this problem.

Co-authored-by: Igor Munkin <imun@tarantool.org>

NO_DOC=infra
NO_CHANGELOG=infra
NO_TEST=infra

Part of #6923

NO_TEST=docrequest

@TarantoolBot document
Title: Document interval arithmetic

Interval arithmetic
-------------------

If we need to shift date values by the given period of time we call either
modifier methods (i.e. `:add` or `:sub`) or apply interval arithmetic
using overloaded `+` (__add) or `-` (__sub) methods.

`:add`/`:sub` modify current object, but `__add`/`__sub` create copy of
object for operation result.

In the interval operation we sequentially calculate each interval
subcomponents
heading from largest (year) to smallest (nanosecond):
* `year` - year(s);
* `month` - month(s);
* `week` - week(s);
* `day` - day(s);
* `hour` - hour(s);
* `min` - minute(s);
* `sec` - second(s);
* `nsec` - nanosecond(s).

If results of operation exceed allowed range for any of component then
exception to be raised.

Modifier methods `:add`/`:sub` return `self` object thus it''s possible to
chain their calls together, i.e.

```
-- add 9000 years, 82 months, 5 weeks, 201 days, 183 hours, 292 minutes
-- and 191.001239234 seconds to given date
dt:add{
	year  = 9000,
	month = 82,
	week  = 5,
	day   = 201,

	sec   = 191,
	min   = 292,
	hour  = 183,

	nsec  = 1239234,
}

dt:sub{
	year  = 9000,
	month = 82,
	week  = 5,
	day   = 201,

	sec   = 191,
	min   = 292,
	hour  = 183,

	nsec  = 1239234,
}

-- chaining
dt:add{year = 2}:add{month = 2}:sub{day = 2}

-- create a copy of current date, while moving it to the next day
local dt2 = datetime.new(dt:totable()):add{day = 1}
```

Arithmetic operations
=====================

Date and interval objects may participate in arithmetic operations:
* Sum of 2 intervals is interval object, which fields would be sum of each
  particular components of operands;
* Subtraction is similar to summation above - result is interval object
  where each subcomponent would be result of subtraction of particular
  fields in original operands;
* If you add date and interval then result is a date. Addition to be
  performed in a determined order from largest component (i.e. year) to
  smallest (nanosecond);
* Subtraction of dates to produce an interval object. Difference of 2 time
  moments is performed not as difference of epoch seconds, but as
  difference of all subcomponents (i.e. years, months, days, hours,
  minutes and seconds);
* Untyped table object may be used in each context where typed date or
  interval object used if left operand is typed object with overloaded
  operation of '+' or '-'.

Matrix of *addition* operands eligibility and their result type:

|                     | datetime | interval | table    |
|---------------------|----------|----------|----------|
| **datetime**        |          | datetime | datetime |
| **interval**        | datetime | interval | interval |
| **table**           |          |          |          |

Matrix of *subtraction* operands eligibility and their result type:

|                     | datetime | interval | table    |
|---------------------|----------|----------|----------|
| **datetime**        | interval | datetime | datetime |
| **interval**        |          | interval | interval |
| **table**           |          |          |          |

Date adjustions and leap years
==============================

It''s always tricky to operate with days if we move date between months of
different lengths. The default mode is - the day number in month of
original date should become the same day but not exceed the length of
resultant month.

* 28 February of non-leap year if added +1 year should become 28 february
  of a leap year;
* Addition of year to the 29 February of a leap year would result with 28
  February of a non-leap year;

The general rule is as following: addition of months to the date should
produce (if possible) the same day number, if this number is not exceeding
number of days in resultant month. Otherwise it produces the last day in
month.

* 31 january + 1 month = 28 or 29 february;
* 30 january + 1 month = 28 or 29 february;
* 29 february + 1 month = 29 march;
* 31 march + 1 month = 30 april.

Optionally you may prefer to use "accountant" logics of operations when
month operations (addition or subtraction) should leave last day in month
as last day, i.e.:

* 31 january + 1 month = 28 or 29 february (depending on leap year);
* 29 february + 1 month = 31 march;
* 31 march + 1 month = 30 april;
* 30 april + 1 month = 31 may.

- 28 february 2001 + 1 month = 28 march 2001;
- february 2004 + 1 month = 28 марта 2004;

This adjustment option named `adjust` may be passed as additional argument
to `:add`/`:sub` methods or additional argument to interval constructor
call.

There are 3 supported `adjust` values:

* `none` last day mode is not maintained, if there is overflow then value
  is truncated to the maximum possible value in month (corresponding to
  the c-dt `DT_LIMIT`). This is default mode if not provided;

```
    -- 29.02.* -> 29.03.*
    dt:add( {month = 1, adjust = "none" } )
```

* `last` last day mode ("accountant" mode) maintained. i.e. last day in
  original month should stay last day in resultant month. This corresponds
   to `c-dt` `DT_SNAP` mode;

```
-- 28.02.2001 -> 31.03.2001 -- last day in Feb 2001
-- 28.02.2004 -> 28.03.2004 -- not a last day in Feb => no abjustments
-- 29.02.2004 -> 31.03.2001 -- last day in Feb 2004
dt:add( {month = 1,  adjust = "last" } )
```

* `excess` overflow to the next month performed. According to `c-dt`
  `DT_EXCESS` rules.

Stringization
=============

Intervals show each their subcomponents as negative or positive value.
Seconds and nanoseconds normalized to the human-interpretable form.

* '+1 seconds';
* '+12 hours, 10 minutes, 30 seconds';
* '-20 months, -10 weeks, -8 hours, -10 minutes, -30 seconds';
* '-5000000 years, -20 months, -10 weeks, -10 minutes, -30 seconds';

We may overflow supported years range if we proceed
(multiple times) interval addition or subtraction operations.
At the end of add/sub we check all interval subcomponents
on validity of their value. Result of this check is returned
in the encoded value to the Lua side, where less than 0 means
underflow in some component, and greater than 0 overflow in
subcomponent.

Part of #6923

NO_DOC=fix
NO_CHANGELOG=fix

Split single sec field in the datetime_interval into multiple subfields,
i.e. week, day, hour, min, sec. Make sure that whatever we enter in the
constructor we get similarly visualized as textual representation

Lua implementation of datetime_totable has been converted to C, which
allows to use it for datetime values decomposing in datetimes
subtraction. It uses per component subtraction for calculating of a
resultant interval.

Part of #6923

NO_DOC=refactoring
NO_CHANGELOG=refactoring

Created C implementation for the rest of datetime/interval operations
and call them via FFI. We need it for later Olson integration.

Part of #6923

NO_DOC=refactoring
NO_CHANGELOG=refactoring
NO_TEST=refactoring, tests left intact

Convert Lua implementation of datetime_increment_by to C from their
Lua variant.

Part of #6923

NO_DOC=refactoring
NO_CHANGELOG=refactoring
NO_TEST=refactoring, tests left intact

Part of #6923

NO_DOC=refactoring
NO_CHANGELOG=refactoring
NO_TEST=refactoring, tests left intact

Part of #6923

NO_DOC=internal
NO_CHANGELOG=internal
NO_TEST=refactoring, tests left intact

Simplify datetime interval data handling in Lua module:
* everytime we used to pass year, month, day, hour and second we simply
  pass aggregate containing those values.

Part of #6923

NO_DOC=refactoring
NO_CHANGELOG=refactoring
NO_TEST=refactoring, tests left intact

This patch fixes an error that occurred when a UUID index was created
on a SCALAR field or a SCALAR index was created on a UUID field.

Follow-up #6042

NO_DOC=Follow up.
NO_CHANGELOG=Follow up.

So that we can reuse it for online space upgrade.

NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring

This is needed to factor out the function that decodes space format so
that it can be used for online space upgrade. It's not a big deal,
because we already use ER_WRONG_SPACE_OPTIONS if space options specified
on space creation/alter are wrong so using ER_WRONG_SPACE_FORMAT would
only be consistent.

NO_DOC=minor change in error message
NO_CHANGELOG=minor change in error message