[Backport 2.x] Add timestamp pinning service and scheduler to update in-memory state

[opensearch-trigger-bot]

Backport 1717b55 from #15180.

[github-actions]

✅ Gradle check result for 7cd1ed9: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 46.95122% with 87 lines in your changes missing coverage. Please review.

Project coverage is 71.63%. Comparing base (0b681c7) to head (7cd1ed9).
Report is 1 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
...remotestore/RemoteStorePinnedTimestampService.java	31.89%	77 Missing and 2 partials ⚠️
...h/gateway/remote/model/RemotePinnedTimestamps.java	78.78%	5 Missing and 2 partials ⚠️
...te/model/RemoteStorePinnedTimestampsBlobStore.java	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #15547      +/-   ##
============================================
- Coverage     71.66%   71.63%   -0.03%     
- Complexity    63697    63773      +76     
============================================
  Files          5235     5238       +3     
  Lines        298161   298324     +163     
  Branches      43412    43423      +11     
============================================
+ Hits         213673   213718      +45     
- Misses        66580    66721     +141     
+ Partials      17908    17885      -23     

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