[Backport 2.0] Adds release notes for 2.0.0

[opensearch-trigger-bot]

Backport a0f81d1 from #367

[codecov-commenter]

Codecov Report

Merging #368 (a0f81d1) into 2.0 (ca0f787) will decrease coverage by 0.08%.
The diff coverage is 47.33%.

❗ Current head a0f81d1 differs from pull request most recent head e6dfad6. Consider uploading reports for the commit e6dfad6 to get more accurate results

@@             Coverage Diff              @@
##                2.0     #368      +/-   ##
============================================
- Coverage     75.25%   75.17%   -0.09%     
+ Complexity     2159     2155       -4     
============================================
  Files           263      263              
  Lines         12413    12413              
  Branches       1974     1974              
============================================
- Hits           9342     9331      -11     
- Misses         1984     1994      +10     
- Partials       1087     1088       +1     

Impacted Files	Coverage Δ
...nt/indexstatemanagement/ManagedIndexCoordinator.kt	68.71% <18.18%> (-0.59%)	⬇️
...ent/indexstatemanagement/step/shrink/ShrinkStep.kt	36.26% <36.26%> (ø)
...exstatemanagement/step/shrink/WaitForShrinkStep.kt	42.00% <36.36%> (ø)
...exstatemanagement/step/shrink/AttemptShrinkStep.kt	60.71% <37.50%> (ø)
...atemanagement/step/shrink/WaitForMoveShardsStep.kt	49.23% <55.81%> (ø)
...atemanagement/step/shrink/AttemptMoveShardsStep.kt	60.42% <65.45%> (ø)
...ent/indexstatemanagement/util/ManagedIndexUtils.kt	77.87% <83.33%> (ø)
...xmanagement/indexstatemanagement/util/StepUtils.kt	87.64% <100.00%> (ø)
...nt/indexstatemanagement/model/destination/Chime.kt	55.55% <0.00%> (-22.23%)	⬇️
...gement/indexstatemanagement/action/ShrinkAction.kt	69.11% <0.00%> (-2.95%)	⬇️
... and 12 more

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