Actualize changelog based on GitHub release pages changelogs. Some
entries were skipped since they are not relevant to modern packages.
Versions 1.8.1 and 2.0.4 changelogs were merged to 2.1.1 changelog.

Part of #6397

This patch extends the 'integration.yml' workflow and adds a new
workflow call for running tests to verify integration between tarantool
and the expiration module.

Part of #5265
Part of #6056
Closes #6528

This commit fixes the following failure:

```
[028] --- wal_off/snapshot_stress.result	Fri Jun  5 06:49:36 2020
[028] +++ wal_off/snapshot_stress.reject	Fri Oct 16 13:48:23 2020
[028] @@ -375,7 +375,7 @@
[028]  ...
[028]  snaps_find_status;
[028]  ---
[028] -- snaps found
[028] +- where are my snapshots?
[028]  ...
[028]  snapshot_check_failed = false
[028]  while #snaps > initial_snap_count do
[028]
```

It happens, because the fiber making snapshots is started after worker
fibers and it works until all worker fibers are done so it might occur
that it doesn't make any snapshots. Fix this by replacing the while-loop
with a repeat-loop, thus ensuring that the worker fiber makes at least
one snapshot.

Closes #5431

Just need to replace scoped guards with labels and add struct keyword to
the sockaddr types.

While we are at it, replace malloc with xmalloc in coio_fill_addrinfo -
we don't check if the returned valued is NULL anyway.

There are just a few places outside coio.cc and coio_buf.h where these
functions are used directly (most users use helpers from coio_buf.h or
xrow_io.h): popen, console, applier.

This is a step towards conversion of coio to C.

This commit makes coio_stat_stat_timeout, coio_waitpid, and
coio_service_start exception-free. None of the functions is used
anywhere in the code except for tests.

This is a step towards conversion of coio to C.

Note, the only place where coio_connect is used is applier_connect,
while coio_accept isn't used anywhere.

This is needed to convert the net.box state machine to C.

So that users that don't have an uri at hand can use it.

This is needed to convert the net.box state machine to C.

Closes #3174

@TarantoolBot document
Title: Field type ANY in SQL

Properties of type ANY in SQL:
1) typeof() with an argument of type ANY returns "any";
2) any value of any type can be implicitly and explicitly cast to the ANY type;
3) a value of type ANY cannot be implicitly cast to any other type;
4) a value of type ANY cannot participate in arithmetic, bitwise, comparison,
   and concationation operations.

After this patch, the built-in SQL function implementation definitions
will use field_type_MAX to indicate that they accept values of any type,
instead of FIELD_TYPE_ANY.

Part of #3174

Prior to this patch, in some cases a struct Expr value with an opcode
TK_INTEGER could have field type ANY. This patch sets such values to the
INTEGER field type.

Part of #3174

This patch extends the 'integration.yml' workflow and adds a new
workflow call for running tests to verify integration between tarantool
and the tarantool-php/queue connector.

Part of #5265
Part of #6056
Closes #6595

This patch forces SQL built-in function implementations to accept
'const struct Mem *' instead of just 'struct Mem *'.

Needed for #4145

This patch removes the MEM_Term flag, because after changes in the SQL
built-in functions, this flag is no longer used.

Needed for #4145

This patch removes the MEM_Dyn flag, because after changes in the SQL
built-in functions, this flag is no longer used.

Needed for #4145

Some of the code is no longer used after changes in the SQL built-in
functions. This patch removes part of the unused code.

Needed for #4145

Part of #4145

Part of #4145

Part of #4145

Part of #4145

This patch refactors UUID() function. Also, UUID(NULL) now returns NULL.

Part of #4145

Part of #4145

Part of #4145

Part of #4145

Part of #4145

This patch refactors RANDOMBLOB() function. Also, RANDOMBLOB(0) now
returns empty string.

part of #4145

Part of #4145

Part of #4145

Part of #4145

Part of #4145

Part of #4145

The CHAR() function now uses the ICU macro to get characters.

Part of #4145

Part of #4145

This patch makes SUBSTR() work according to ANSI rules for SUBSTRING()
function. Also, SUBSTR() can now work correctly with large INTEGER
values. The SUBSTR() syntax has not changed.

Part of #4145

@TarantoolBot document
Title: SUBSTR() function

SUBSTR() now works according to the ANSI rules for SUBSTRING().

Rules for SUBSTR() with 2 arguments:
1) let the first argument be VALUE, and the second argument be START;
2) VALUE should be STRING or VARBINARY, START should be INTEGER;
3) if any of arguments is NULL, NULL is returned;
4) let POS be MAX(START - 1, 0), END be length of the VALUE;
5) if POS >= END, the result is empty string;
6) if POS < END, the result will be substring of VALUE, starting from
   the position POS to the position END.

Rules for SUBSTR() with 3 arguments:
1) let the first argument be VALUE, the second argument be START, and
   the third argument be LENGTH;
2) VALUE should be STRING or VARBINARY, START and LENGTH should be
   INTEGERs;
3) if any of arguments is NULL, NULL is returned;
4) if LENGTH < 0, an error is thrown;
5) let POS be MAX(START - 1, 0), END be START + LENGTH - 1;
6) if POS >= END, the result is empty string;
7) if POS < END, the result will be substring of VALUE, starting from
   the position POS to the position END.

This patch is a refactoring of POSITION(). In addition, VARBINARY
arguments can now be used in this function. In addition, POSITION() now
uses ICU functions instead of self-created.

Part of #4145

This patch refactoring TRIM() and fixes an issue with incorrect trimming
of some VARBINARY values. Also, TRIM() now use ICU functions instead of
self-created.

Part of #4415

Part of #4145

Part of #4145

The CHAR_LENGTH() and CHARACTER_LENGTH() functions now use ICU functions
to determine the length of a string.

Part of #4145

@TarantoolBot document
Title: Invalid UTF-8 values and ICU

Invalid UTF-8 values may be handled differently depending on the ICU
version. For example, for this request:
```
SELECT CHAR_LENGTH(CAST(x'f0808080' AS STRING));
```

On `centos 7` with `libicu-devel-50.2-4.el7_7.x86_64` the result will
be:
```
tarantool> box.execute([[SELECT CHAR_LENGTH(CAST(x'f0808080' AS STRING));]])
---
- metadata:
  - name: COLUMN_1
    type: integer
  rows:
  - [1]
...
```

On `ubuntu 20.04` with `libicu-dev` version `66.1-2ubuntu2` the result
will be:
```
tarantool> box.execute([[SELECT CHAR_LENGTH(CAST(x'f0808080' AS STRING));]])
---
- metadata:
  - name: COLUMN_1
    type: integer
  rows:
  - [4]
...
```