Add release notes for 1.3.16

[mgodwan]

Description

Add release notes for 1.3.16

Related Issues

Based on https://github.com/opensearch-project/OpenSearch/commits/1.3/

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

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

❕ Gradle check result for f9db33c: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.http.SearchRestCancellationIT.testAutomaticCancellationMultiSearchDuringQueryPhase
      1 org.opensearch.http.SearchRestCancellationIT.testAutomaticCancellationDuringQueryPhase
      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 71.45%. Comparing base (84679de) to head (f9db33c).

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13280      +/-   ##
============================================
- Coverage     71.48%   71.45%   -0.03%     
- Complexity    60670    60677       +7     
============================================
  Files          5040     5040              
  Lines        285456   285456              
  Branches      41338    41338              
============================================
- Hits         204044   203965      -79     
- Misses        64589    64669      +80     
+ Partials      16823    16822       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[reta]

We probably need to clean up the CHANGELOG.md sectoon for [Unreleased 1.3.x]

[mgodwan]

We probably need to clean up the CHANGELOG.md sectoon for [Unreleased 1.3.x]

@reta That would be a different PR directly in 1.3 branch, right? (Since the changelog in main does not track 1.3.x) https://github.com/opensearch-project/OpenSearch/blob/1.3/CHANGELOG.md

I can raise the PR directly against 1.3 in that case once this is merged and backported