This commit makes logger escape prohibited characters in plain format,
to make Tarantool's syslog logging comply with RFC 3164, which states:

> The MSG part of the syslog packet MUST contain visible (printing)
  characters. The code set traditionally and most often used has also
  been seven-bit ASCII in an eight-bit field like that used in the PRI
  and HEADER parts. In this code set, the only allowable characters
  are the ABNF VCHAR values (%d33-126) and spaces (SP value %d32) 1.

It's implemented with inplace escaping for the sake of code simplicity.

Part of tarantool#12006

NO_DOC=later
NO_CHANGELOG=later

This commit makes logger escape prohibited characters in JSON format,
to make Tarantool's syslog logging comply with RFC 3164, which states:

> The MSG part of the syslog packet MUST contain visible (printing)
  characters. The code set traditionally and most often used has also
  been seven-bit ASCII in an eight-bit field like that used in the PRI
  and HEADER parts. In this code set, the only allowable characters
  are the ABNF VCHAR values (%d33 - 126) and spaces (SP value %d32) 1.

Simple `json_escape_inplace` in the end cannot be used for json
escaping, as it was done for plain format, since it'll corrupt the
structure of the message and it won't be possible to decode it after
that.

Closes tarantool#12006

@TarantoolBot document
Title: Document the RFC 3164 syslog format compliance
Since: 3.6.1

Documents:
  * https://www.tarantool.io/en/doc/latest/reference/configuration/configuration_reference/#audit-log-syslog
  * https://www.tarantool.io/en/doc/latest/admin/logs/#log-destination
  * https://www.tarantool.io/en/doc/latest/reference/reference_lua/log/
  * https://www.tarantool.io/en/doc/latest/reference/configuration/#confval-log

The syslog format is compliant with
[RFC 3164](https://www.rfc-editor.org/rfc/rfc3164.html). However, the
length of the message can be up to 16 * 1024 bytes.

The RFC 5424 expects the syslog message header to be formatted as:

> <165>1 2003-10-11T22:14:15.003Z mymachine.example.com
  evntslog - ID47 [exampleSDID@32473 iut="3" eventSource=
  "Application" eventID="1011"] BOMAn application
  event log entry...

Our syslog message header doesn't comply with it, users should configure
syslog parser according to RFC 3164, so let's remove mention of another
one from the comments.

Follow-up tarantool#12006

NO_DOC=comment
NO_TEST=comment
NO_CHANGELOG=comment