[Backport 2.x] Snapshot _status API to return correct status for partial snapshots (#12812)

[aggarwalShivani]

Description

Backporting #12812 to 2.x branch.

Related Issues

Resolves #7952

Check List

• New functionality includes testing.
  • All tests pass
• ~[ ] New functionality has been documented. ~
  • [ ] New functionality has javadoc added
• Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)
• [ ] Public documentation issue/PR created

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[github-actions]

✅ Gradle check result for 328c0bb: SUCCESS

[github-actions]

❌ Gradle check result for 20a9a5b: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❕ Gradle check result for a1323f3: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=indices.get_field_mapping/20_missing_field/Return empty object if field doesn't exist, but index does}

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

[codecov]

Codecov Report

Attention: Patch coverage is 37.50000% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 71.15%. Comparing base (0dd892c) to head (a1323f3).
Report is 151 commits behind head on 2.x.

Files	Patch %	Lines
...va/org/opensearch/cluster/SnapshotsInProgress.java	50.00%	2 Missing and 1 partial ⚠️
...apshots/status/TransportSnapshotsStatusAction.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #13260      +/-   ##
============================================
- Coverage     71.28%   71.15%   -0.13%     
- Complexity    60145    60615     +470     
============================================
  Files          4957     5004      +47     
  Lines        282799   285411    +2612     
  Branches      41409    41729     +320     
============================================
+ Hits         201591   203083    +1492     
- Misses        64189    65210    +1021     
- Partials      17019    17118      +99     

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[aggarwalShivani]

❕ Gradle check result for a1323f3: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=indices.get_field_mapping/20_missing_field/Return empty object if field doesn't exist, but index does}

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

Existing flaky issue ->
MixedClusterClientYamlTestSuiteIT.test() #2440