Bump 2.x to 2.16.0

[peterzhuamazon]

Description

Bump 2.x to 2.16.0

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 7af88db: 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?

[github-actions]

❕ Gradle check result for 7af88db: UNSTABLE

• TEST FAILURES:

      1 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 71.35%. Comparing base (0dd892c) to head (7af88db).
Report is 356 commits behind head on 2.x.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #14216      +/-   ##
============================================
+ Coverage     71.28%   71.35%   +0.06%     
- Complexity    60145    62026    +1881     
============================================
  Files          4957     5094     +137     
  Lines        282799   292031    +9232     
  Branches      41409    42549    +1140     
============================================
+ Hits         201591   208368    +6777     
- Misses        64189    66112    +1923     
- Partials      17019    17551     +532     

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