[Remote Store] Fix shards condition in stats api

[ashking94]

Description

Remote store stats api returns no response if coordinator node does not contain remote enabled shard

If lets say we have 3 nodes - N1, N2 and N3 and there is remote store enabled index index1 with 1 shard (on N1) and 0 replica, then if we call remotestore stats api on N1, it returns the stats. If we call the api on N2 or N3, it returns empty result.

In this PR, we check the index setting by reading the cluster state since the indicesService does not hold the shards that don't reside on underlying coordinator node.

Related Issues

Resolves #7738

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/16234/
• CommitID: 01b1996

[codecov]

Codecov Report

Merging #7739 (392bb9d) into main (8e2d059) will increase coverage by 0.13%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main    #7739      +/-   ##
============================================
+ Coverage     70.67%   70.81%   +0.13%     
- Complexity    56095    56195     +100     
============================================
  Files          4680     4680              
  Lines        266079   266080       +1     
  Branches      39074    39074              
============================================
+ Hits         188062   188435     +373     
+ Misses        62029    61644     -385     
- Partials      15988    16001      +13     

Impacted Files	Coverage Δ
...testore/stats/TransportRemoteStoreStatsAction.java	45.94% <100.00%> (+4.27%)	⬆️

... and 492 files with indirect coverage changes

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.indices.replication.SegmentReplicationIT.testScrollCreatedOnReplica

• URL: https://build.ci.opensearch.org/job/gradle-check/16239/
• CommitID: 02079a8
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[sachinpkale]

PR description does not provide details on what we are changing. Please add 1-2 lines for the same.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.search.SearchWeightedRoutingIT.testSearchAggregationWithNetworkDisruption_FailOpenEnabled
      1 org.opensearch.indices.replication.SegmentReplicationIT.testScrollCreatedOnReplica

• URL: https://build.ci.opensearch.org/job/gradle-check/16362/
• CommitID: 392bb9d
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.