PR #104265 - util/log: MVP of customizable tz support for the datetime field

[cockroach-teamcity]

Exalate commented:

Related PR: cockroachdb/cockroach#104265
Commit: cockroachdb/cockroach@24e577a
Fixes: CRDB-5594 CRDB-19901

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Release note (cli change): The json log output format now recognizes
the extra format option datetime-timezone which selects which timezone
to use when formatting the datetime field.
datetime-timezone must be combined with datetime-format because
the default value for the latter option is none, i.e. datetime
is not produced by default.

For example:

sinks:
  fluent-groups:
     custom-json:
        format: json
        format-options: {datetime-format: rfc3339, datetime-timezone: America/New_York}

Jira Issue: DOC-8100