Logs Panel: Refactor style generation to improve rendering performance

[matyax]

What is this feature?

This PR refactors how we generate and share styles in logs-related components. The main changes are:

• Parse styles shared by rows and other components once in LogsRow, then pass them as a prop.
• The dynamic css that sets the row color related with the level of a log has been simplified and delegated to getLogLevelStyles().
• Individual getStyles() calls made by children components of a LogRow have been moved to getLogRowStyles().

A minor change included in this PR is a TimeZone import deprecation fix.

Which issue(s) does this PR fix?:

Part of #60687
Part of #63030

Special notes for your reviewer:

The tests for this PR have been performed in the Explore page.

The changes in this branch have been validated using the browser profiler and the React profiler before submission, to ascertain that there was a performance gain from each change. Individual changes have been also ran through the profiler, including a refactor of LogRow using functional components which was not included because it had no impact.

Avoiding the use of cx() and calls to getLogLevelStyles() have been tested and showed no visible performance improvements.

Measurements in the main branch:

Measurements in this feature branch:

The underlying functionality should, obviously, remain intact.

[svennergr]

Nice work. Left a few comments. WDYT about adding the usage of the useStyles2 hook when calling getLogLevelStyles and getLogRowStyles?

[matyax]

It's worth mentioning that the measurements and tests for this PR were done in the Explore page. Will follow up with what I see in Dashboards.