[Segment Replication] Clean up SegmentReplicationTargetService only hold the state of last completed replications

[mch2]

Description

This is a minor refactor to SegmentReplicationTargetService. After a replication event completes we store a reference to the latest completed SegmentReplicationTarget for the purpose of returning metrics. These metrics rely on the SegmentReplicationState object alone, not the entire target which can be cleaned up.

Related Issues

N/A

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

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]

Compatibility status:

Checks if related components are compatible with change 349a5fe

Incompatible components

Incompatible components: [https://github.com/opensearch-project/performance-analyzer.git]

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/opensearch-oci-object-storage.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/neural-search.git]

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/29420/
• CommitID: 349a5fe
  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 (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/29422/
• CommitID: 349a5fe
  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 (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/29426/
• CommitID: 349a5fe
  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?

[mch2]

• https://build.ci.opensearch.org/job/gradle-check/29420/

#9499
#11063

[mch2]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/29426/
• CommitID: 349a5fe
  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?

#10903

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.remotestore.multipart.RemoteStoreMultipartIT.testOverriddenBufferInterval
      1 org.opensearch.remotestore.multipart.RemoteStoreMultipartIT.testAsyncDurabilityThrowsExceptionWhenRestrictSettingTrue

• URL: https://build.ci.opensearch.org/job/gradle-check/29483/
• CommitID: 349a5fe
  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

Merging #11043 (349a5fe) into main (63aff16) will not change coverage.
Report is 5 commits behind head on main.
The diff coverage is 66.66%.

@@            Coverage Diff            @@
##               main   #11043   +/-   ##
=========================================
  Coverage     71.29%   71.29%           
- Complexity    58742    58789   +47     
=========================================
  Files          4872     4872           
  Lines        276777   276777           
  Branches      40240    40240           
=========================================
  Hits         197316   197316           
- Misses        62943    62992   +49     
+ Partials      16518    16469   -49     

Files	Coverage Δ
...s/replication/SegmentReplicationTargetService.java	55.60% <66.66%> (ø)

... and 481 files with indirect coverage changes