[WIP] SOLR-17040 UpdateLog refactor to use read/write locks

[stillalex]

https://issues.apache.org/jira/browse/SOLR-17040

Description

PR for review/discussion. see Jira for current benchmark results.

Solution

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Tests

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

Checklist

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• 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 main branch.
• I have run ./gradlew check.
• I have added tests for my changes.
• I have added documentation for the Reference Guide

[stillalex]

closing. benchmarks do not show improvements on this change.