Add restriction to have a single repository with shallow snapshot v2 setting

[sachinpkale]

Description

• Shallow snapshot V2 setting is introduced to enable creating snapshot which uses pinned timestamp functionality of remote store.
• As pinned timestamps are created at cluster level, if multiple repositories enable this feature and create snapshots, clean-up of data from remote store on snapshot deletion becomes tricky and we may end up leaving zombie data in the remote store.
• To avoid this, in this PR, we have added a restriction to have only 1 repository with shallow snapshot V2 enabled.
• In order to enable shallow snapshot V2 setting on another repository, we need to disable this setting on the previously enabled repository as well as delete any snapshots that are created with the previous repo.
• We will ease up this restriction in the upcoming releases.

Related Issues

• [BUG] Missing validations in shallow snapshot V2 repo creation #15913

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

✅ Gradle check result for 1526597: SUCCESS

[github-actions]

❕ Gradle check result for c57c9c2: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.remotestore.RemoteStoreStatsIT.testNonZeroPrimaryStatsOnNewlyCreatedIndexWithZeroDocs
      1 org.opensearch.remotestore.RemoteStoreStatsIT.testDownloadStatsCorrectnessSinglePrimarySingleReplica

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[github-actions]

✅ Gradle check result for 0d86005: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 86.36364% with 6 lines in your changes missing coverage. Please review.

Project coverage is 72.01%. Comparing base (92d7fe8) to head (de752dc).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
...g/opensearch/repositories/RepositoriesService.java	80.76%	4 Missing and 1 partial ⚠️
...remotestore/RemoteStorePinnedTimestampService.java	94.44%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #15901      +/-   ##
============================================
+ Coverage     71.90%   72.01%   +0.10%     
- Complexity    64216    64311      +95     
============================================
  Files          5272     5272              
  Lines        300597   300636      +39     
  Branches      43440    43449       +9     
============================================
+ Hits         216151   216499     +348     
+ Misses        66680    66422     -258     
+ Partials      17766    17715      -51     

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[github-actions]

✅ Gradle check result for de752dc: SUCCESS