[Backport 2.x] docCountError must be 0 for shard level reduce

[opensearch-trigger-bot]

Backport db768d1 from #9246.

[opensearch-trigger-bot]

Compatibility status:

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

BUILD SUCCESSFUL in 31m 15s

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/22559/
• CommitID: 6974ecc

[codecov]

Codecov Report

Merging #9282 (6974ecc) into 2.x (c568386) will decrease coverage by 0.08%.
Report is 5 commits behind head on 2.x.
The diff coverage is 91.46%.

@@             Coverage Diff              @@
##                2.x    #9282      +/-   ##
============================================
- Coverage     70.85%   70.78%   -0.08%     
+ Complexity    57499    57474      -25     
============================================
  Files          4758     4758              
  Lines        271801   271785      -16     
  Branches      40090    40087       -3     
============================================
- Hits         192590   192373     -217     
- Misses        62700    62930     +230     
+ Partials      16511    16482      -29     

Files Changed	Coverage Δ
...rc/main/java/org/opensearch/index/store/Store.java	80.69% <ø> (+0.03%)	⬆️
...ch/indices/recovery/PeerRecoveryTargetService.java	55.22% <0.00%> (+2.28%)	⬆️
...earch/aggregations/bucket/terms/InternalTerms.java	87.50% <50.00%> (ø)
...in/java/org/opensearch/index/shard/IndexShard.java	68.09% <85.71%> (-0.69%)	⬇️
...rg/opensearch/index/engine/ReplicaFileTracker.java	91.66% <91.66%> (ø)
.../opensearch/index/engine/NRTReplicationEngine.java	78.08% <100.00%> (+0.37%)	⬆️
...earch/index/store/RemoteSegmentStoreDirectory.java	87.70% <100.00%> (ø)
...ices/replication/RemoteStoreReplicationSource.java	90.90% <100.00%> (+0.16%)	⬆️
.../indices/replication/SegmentReplicationTarget.java	89.00% <100.00%> (-0.72%)	⬇️

... and 496 files with indirect coverage changes