[Backport 2.3] Added 2.3 release notes.

[opensearch-trigger-bot]

Backport f4a7a41 from #551

[codecov-commenter]

Codecov Report

Merging #555 (f4a7a41) into 2.3 (b7c5f1f) will increase coverage by 0.03%.
The diff coverage is 40.00%.

❗ Current head f4a7a41 differs from pull request most recent head 6a231c3. Consider uploading reports for the commit 6a231c3 to get more accurate results

@@             Coverage Diff              @@
##                2.3     #555      +/-   ##
============================================
+ Coverage     76.71%   76.75%   +0.03%     
  Complexity      176      176              
============================================
  Files           166      166              
  Lines          8370     8370              
  Branches       1232     1232              
============================================
+ Hits           6421     6424       +3     
- Misses         1343     1344       +1     
+ Partials        606      602       -4     

Impacted Files	Coverage Δ
...nationmigration/DestinationMigrationCoordinator.kt	68.08% <0.00%> (+6.38%)	⬆️
...lin/org/opensearch/alerting/alerts/AlertIndices.kt	69.75% <66.66%> (ø)
...destinationmigration/DestinationConversionUtils.kt	68.88% <0.00%> (-1.12%)	⬇️
...ing/model/destination/DestinationContextFactory.kt	75.00% <0.00%> (ø)
...ain/kotlin/org/opensearch/alerting/AlertService.kt	78.46% <0.00%> (+0.47%)	⬆️

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