SOLR-15104: add timestamp in default gc_log name

[interma]

Description

https://issues.apache.org/jira/browse/SOLR-15104

When restarting Solr, it will overwrite the gc log, this behavior is not friendly for debugging OOM issues.

Solution

Add timestamp in default gc_log name, so it doesn't overwrite the previous one.

Tests

Please describe the tests you've developed or run to confirm this patch implements the feature or solves the problem.

Checklist

Please review the following and check all that apply:

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• I have created a Jira issue and added the issue ID to my pull request title.
• I have given Solr maintainers access to contribute to my PR branch. (optional but recommended)
• I have developed this patch against the master branch.
• I have run ./gradlew check.
• I have added tests for my changes.
• I have added documentation for the Ref Guide (for Solr changes only).