[Bugfix] [Tiered Caching] Fixes issues when integrating tiered cache with disk cache

[peteralfonsi]

Description

Fixes issues that prevented us from using the tiered spillover cache with EhcacheDiskCache as the disk cache:

• TSC was not correctly passing serializers to its disk cache, broken since 2.14
• Ehcache plugin was missing slf4j dependency in main, but had it in 2.x branch
• Ehcache plugin was missing permissions and wasn't properly using AccessController.doPrivileged to run its code that required those permissions. Broken since 2.13

These issues weren't caught in automated testing since the TSC lives in a module and the disk cache lives in a separate plugin, so we couldn't IT them together and the issues were only found during manual testing. Confirmed that after these fixes are in place, we can use the feature as desired using:

./gradlew run -Dtests.opensearch.opensearch.experimental.feature.pluggable.caching.enabled=true -Dtests.opensearch.indices.requests.cache.store.name=tiered_spillover -Dtests.opensearch.indices.requests.cache.tiered_spillover.onheap.store.name=opensearch_onheap -Dtests.opensearch.indices.requests.cache.tiered_spillover.disk.store.name=ehcache_disk -Dtests.opensearch.indices.requests.cache.tiered_spillover.disk.store.policies.took_time.threshold=0ms -PinstalledPlugins="['cache-ehcache']" -Dtests.opensearch.indices.requests.cache.ehcache_disk.storage.path="/Volumes/workplace/opensearch/OpenSearch/build/testclusters/runTask-0/data/nodes/0/indices/request_cache"

I've bundled these bugfixes together, as we can't really confirm any one of the fixes works until the manual test runs correctly, which requires all of the fixes.

Related Issues

Part of tiered caching

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
    - [N/A] API changes companion pull request created.
• Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)
• Commits are signed per the DCO using --signoff
  [N/A] Commit changes are listed out in CHANGELOG.md file (See: Changelog)
  [N/A] Public documentation issue/PR created

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[github-actions]

❌ Gradle check result for 7e5f8e0: FAILURE

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[github-actions]

❌ Gradle check result for c470752: FAILURE

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[github-actions]

❌ Gradle check result for d7118d1: FAILURE

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[github-actions]

❕ Gradle check result for ecfb104: UNSTABLE

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

Attention: Patch coverage is 84.61538% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 71.55%. Comparing base (b15cb0c) to head (ecfb104).
Report is 303 commits behind head on main.

Files	Patch %	Lines
.../opensearch/cache/store/disk/EhcacheDiskCache.java	83.78%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13784      +/-   ##
============================================
+ Coverage     71.42%   71.55%   +0.12%     
- Complexity    59978    61137    +1159     
============================================
  Files          4985     5059      +74     
  Lines        282275   287526    +5251     
  Branches      40946    41646     +700     
============================================
+ Hits         201603   205725    +4122     
- Misses        63999    64835     +836     
- Partials      16673    16966     +293     

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