[Backport 2.x] Separating remote download and publication stats

[opensearch-trigger-bot[bot]]

Backport b1a7743b83913ebe0c40744131c5996608e324a0 from #16682.

[github-actions[bot]]

:white_check_mark: Gradle check result for 321afe62faaea70963136743a9dcd31ec4ea7505: SUCCESS

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 69.62963% with 41 lines in your changes missing coverage. Please review.

Project coverage is 71.74%. Comparing base (674edb0) to head (321afe6).

Files with missing lines	Patch %	Lines
...arch/gateway/remote/RemoteClusterStateService.java	73.38%	16 Missing and 17 partials :warning:
...nsearch/gateway/remote/RemotePersistenceStats.java	0.00%	4 Missing :warning:
...opensearch/gateway/remote/RemoteDownloadStats.java	40.00%	3 Missing :warning:
...ster/coordination/PublicationTransportHandler.java	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 2.x #16696 +/- ## ============================================ - Coverage 71.91% 71.74% -0.18% + Complexity 65434 65355 -79 ============================================ Files 5314 5314 Lines 305217 305242 +25 Branches 44474 44475 +1 ============================================ - Hits 219500 218998 -502 - Misses 67415 67910 +495 - Partials 18302 18334 +32 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

---

🚨 Try these New Features:

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