util/log: new output format 'crdb-v2'

[jseldess]

PR: cockroachdb/cockroach#59087

From release notes:

The default output format for file-group and stderr sinks has been changed to crdb-v2. This new format is non-ambiguous and makes it possible to reliably parse log files. Refer to the format's documentation for details. Additionally, it prevents single log lines from exceeding a large size; this problem is inherent to the crdb-v1 format and can prevent cockroach debug zip from retrieving v1 log files. The new format has also been designed so that existing log file analyzers for the crdb-v1 format can read entries written the new format. However, this conversion may be imperfect. Refer to the new format's documentation for details. In case of incompatibility, users can force the previous format by using format: crdb-v1 in their logging configuration. [#59087][#59087] {% comment %}doc{% endcomment %}

[taroface]

Closed by #10273.