datetime: Olson timezones changelog and doc request

Use Olson/IANA tzdata for timezone handling in datetime string.

Closes of #6751

NO_TEST=doc

@TarantoolBot document
Title: Document timezone support

Timezones support
-----------------

Tarantool uses IANA tzdata aka Olson DB facilities for timezone
resolution at the moment of parsing of datetime literals or while
parsing `tz` attribute in constructor, or `:set{}` method call.

In addition to the `tzoffset` we provided before, we now define
`tzindex`, the unique index assigned by Tarantool to each known IANA
timezone.

```lua
date = require 'datetime'

tarantool> T = date.parse '2022-01-01T00:00 Europe/Moscow'

tarantool> T.tzindex
---
- 947
...

tarantool> T.tzoffset
---
- 180
...

tarantool> T.tz
---
- Europe/Moscow
...
```

Now `date.isdst` field (alone and as part of `:totable()` table) is
correctly calculated using `tzindex` and attributes of the selected
timezone in the Olson DB timezone.

```
tarantool> date.parse('2004-06-01T00:00 Europe/Moscow').isdst
---
- true
...

tarantool> date.parse('2004-12-01T00:00 Europe/Moscow'):totable()
---
- sec: 0
  min: 0
  yday: 336
  day: 1
  nsec: 0
  isdst: false
  wday: 4
  tzoffset: 180
  month: 12
  year: 2004
  hour: 0
...

```

All timezone names and abbreviations, known to the current Tarantool
version are available via `datetime.TZ` bidirectional array.

```lua
print(date.TZ['Europe/Moscow']) -- 947
print(date.TZ[947]) -- Europe/Moscow
```

Limitations
-----------

There were moments in past history, when local mean time in some
partcular zone used timezone offset not representable in whole
minutes, but rather in seconds, i.e. in Moscow before 1918 there
used to be offset +2 hours 31 minutes and 19 seconds. Please see
Olson dump for this period

```
$ ./src/lib/tzcode/install/usr/bin/zdump -c1880,1918 -i Europe/Moscow

TZ="Europe/Moscow"
-       -       +023017 MMT
1916-07-03      00:01:02        +023119 MMT
1917-07-02      00      +033119 MST     1
1917-12-27      23      +023119 MMT
```

Modern tzdata rules do not use such tiny fraction, and all timezones differ
to UTC in units measured in minutes, not seconds. Tarantool datetime uses
minutes internally as units for `tzoffset` so there is some loss of
precision if you try to operate with such ancient timestamps.

(cherry picked from commit 979a8fbd)