Fix flaky test SegmentReplicationIT.testDeleteOperations.

[mch2]

Description

This PR fixes SegmentReplicationIT.testDeleteOperations which can occasionally fail when no docs are indexed. Fixed by ensuring at least one doc is indexed and flagged for deletion. Also reduced the doc count potentially indexed to speed up the test.

Related Issues

N/A

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

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.

[opensearch-trigger-bot]

Compatibility status:

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

BUILD SUCCESSFUL in 23m 16s

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/22403/
• CommitID: 755977f
  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: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/22412/
• CommitID: 755977f

[codecov]

Codecov Report

Merging #9244 (755977f) into main (1162865) will increase coverage by 0.11%.
Report is 3 commits behind head on main.
The diff coverage is 92.50%.

@@             Coverage Diff              @@
##               main    #9244      +/-   ##
============================================
+ Coverage     71.03%   71.15%   +0.11%     
- Complexity    57318    57386      +68     
============================================
  Files          4770     4770              
  Lines        270540   270524      -16     
  Branches      39561    39558       -3     
============================================
+ Hits         192186   192484     +298     
+ Misses        62147    61821     -326     
- Partials      16207    16219      +12     

Files Changed	Coverage Δ
...rc/main/java/org/opensearch/index/store/Store.java	81.12% <ø> (+1.83%)	⬆️
...ch/indices/recovery/PeerRecoveryTargetService.java	53.28% <0.00%> (-4.28%)	⬇️
...in/java/org/opensearch/index/shard/IndexShard.java	69.51% <85.71%> (+0.43%)	⬆️
...rg/opensearch/index/engine/ReplicaFileTracker.java	91.66% <91.66%> (ø)
.../opensearch/index/engine/NRTReplicationEngine.java	74.37% <100.00%> (+0.48%)	⬆️
...earch/index/store/RemoteSegmentStoreDirectory.java	87.54% <100.00%> (-0.33%)	⬇️
...ices/replication/RemoteStoreReplicationSource.java	90.90% <100.00%> (+0.16%)	⬆️
.../indices/replication/SegmentReplicationTarget.java	89.00% <100.00%> (-0.72%)	⬇️

... and 478 files with indirect coverage changes