Added support for search replica to return segrep stats

[vinaykpud]

Description

In this PR we are adding,

• Support for search replica to return its segrep stats
• This doesn't change any of the existing implementation stats calculation for the regular replicas
• For search replicas we are just calculating the stats using the difference between the computed checkpoint in the shard and latest pulled checkpoint from the remote store. So this stat will help to know if any problematic replications in search replica which is taking longer.

Related Issues

Resolves #15534
Related #15306

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 39576c3: null

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 39576c3: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 4.76190% with 60 lines in your changes missing coverage. Please review.

Project coverage is 72.04%. Comparing base (3b4fa0e) to head (39576c3).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
...cation/TransportSegmentReplicationStatsAction.java	0.00%	44 Missing ⚠️
...lication/SegmentReplicationShardStatsResponse.java	0.00%	10 Missing ⚠️
...opensearch/index/SegmentReplicationShardStats.java	0.00%	3 Missing ⚠️
...nsearch/index/SegmentReplicationPerGroupStats.java	0.00%	2 Missing ⚠️
...h/indices/replication/SegmentReplicationState.java	66.66%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #16678      +/-   ##
============================================
- Coverage     72.11%   72.04%   -0.07%     
- Complexity    65192    65196       +4     
============================================
  Files          5318     5318              
  Lines        303903   303967      +64     
  Branches      43970    43980      +10     
============================================
- Hits         219166   219003     -163     
- Misses        66786    67042     +256     
+ Partials      17951    17922      -29     

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

---

🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests