[Snapshot V2] Fix for create snapshot build and test failures

[anshu1106]

Description

This is followup for #15124.

1. This PR fixes :server:japicmp failure found during 2.x backport of the above PR.

2. With existing delimiter :, integ test fails with following error:
   https://build.ci.opensearch.org/job/gradle-check/46330/testReport/junit/org.opensearch.remotestore/RemoteRestoreSnapshotIT/testCreateSnapshotV2WithRedIndex/
   In this PR, we are changing the delimiter from : to __

Related Issues

Resolves #15123

Check List

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

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

❌ Gradle check result for e773ee1: 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 1936f24: 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 67a41c2: 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 462d62d: 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 e380db2: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 71.84%. Comparing base (33be5a9) to head (9d2eb9b).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...in/java/org/opensearch/snapshots/SnapshotInfo.java	0.00%	4 Missing ⚠️
.../org/opensearch/repositories/FilterRepository.java	0.00%	2 Missing ⚠️
...ch/repositories/blobstore/BlobStoreRepository.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #15602      +/-   ##
============================================
- Coverage     71.99%   71.84%   -0.15%     
+ Complexity    63924    63870      -54     
============================================
  Files          5257     5257              
  Lines        298667   298675       +8     
  Branches      43184    43184              
============================================
- Hits         215028   214593     -435     
- Misses        65972    66453     +481     
+ Partials      17667    17629      -38     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-actions]

❌ Gradle check result for 4fc5ed0: 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 9d2eb9b: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.snapshots.DedicatedClusterSnapshotRestoreIT.testSnapshotWithStuckNode
      1 org.opensearch.action.admin.cluster.node.tasks.ResourceAwareTasksTests.testTaskResourceTrackingDuringTaskCancellation

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