[Forwardport] [main] Bump 2.x to 2.15.0 (#13495)

[reta]

Description

Forwardport of #13495 to main

Related Issues

N/A

Check List

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

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[github-actions]

❌ Gradle check result for f13c643: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[reta]

❌ Gradle check result for f13c643: FAILURE

#12197
#10558
#10006

[github-actions]

❌ Gradle check result for f13c643: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[reta]

❌ Gradle check result for f13c643: FAILURE

#9464

[github-actions]

❕ Gradle check result for f13c643: UNSTABLE

• TEST FAILURES:

      2 org.opensearch.cluster.coordination.AwarenessAttributeDecommissionIT.testConcurrentDecommissionAction

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

All modified and coverable lines are covered by tests ✅

Project coverage is 71.45%. Comparing base (b15cb0c) to head (f13c643).
Report is 250 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13506      +/-   ##
============================================
+ Coverage     71.42%   71.45%   +0.03%     
- Complexity    59978    60977     +999     
============================================
  Files          4985     5050      +65     
  Lines        282275   286806    +4531     
  Branches      40946    41552     +606     
============================================
+ Hits         201603   204943    +3340     
- Misses        63999    64915     +916     
- Partials      16673    16948     +275     

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