[AUTO] Add release notes for 3.6.0

[opensearch-ci-bot]

Add release notes for 3.6.0

Borderline Calls

• Fix typo in validFileNameExcludingAsterisk #1608: Placed in Bug Fixes — could also be Maintenance since it's a simple typo fix, but the typo is in a validation function name which constitutes a code defect.
• Update shadow plugin usage #1587: Placed in Infrastructure — borderline with Maintenance, chose Infrastructure because it modifies the build process (Gradle shadow plugin usage) rather than being a routine dependency bump.
• Fix flaky rollup test by stopping jobs before index cleanup #1530: Placed in Bug Fixes — could also be Infrastructure since it fixes a flaky test, but the root cause was a genuine race condition bug in test teardown logic that caused incorrect index mappings.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.58%. Comparing base (f3286ac) to head (354fc31).
⚠️ Report is 1 commits behind head on 3.6.

Additional details and impacted files

@@             Coverage Diff              @@
##                3.6    #1616      +/-   ##
============================================
+ Coverage     76.46%   76.58%   +0.12%     
============================================
  Files           381      381              
  Lines         18069    18069              
  Branches       2503     2503              
============================================
+ Hits          13817    13839      +22     
+ Misses         2987     2967      -20     
+ Partials       1265     1263       -2     

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