Optimise memory for rest cluster health calls with in-line shard aggr…

[SwethaGuptha]

…egations for levels cluster and indices. (#15492)

Description

Backport #15492 to 2.17

[github-actions]

❌ Gradle check result for 67b9165: FAILURE

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?

[gbbafna]

[org.opensearch.indices.settings.SearchOnlyReplicaIT.testFailoverWithSearchReplica_WithoutWriterReplicas](https://build.ci.opensearch.org/job/gradle-check/47474/testReport/junit/org.opensearch.indices.settings/SearchOnlyReplicaIT/testFailoverWithSearchReplica_WithoutWriterReplicas/)
    [org.opensearch.recovery.RelocationIT.testIndexSearchAndRelocateConcurrently {p0={"cluster.indices.replication.strategy":"SEGMENT"}}](https://build.ci.opensearch.org/job/gradle-check/47474/testReport/junit/org.opensearch.recovery/RelocationIT/testIndexSearchAndRelocateConcurrently__p0___cluster_indices_replication_strategy___SEGMENT___/)

Looks like new flaky tests .

[github-actions]

❌ Gradle check result for 67b9165: FAILURE

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 7c54d31: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 93.92265% with 11 lines in your changes missing coverage. Please review.

Project coverage is 71.62%. Comparing base (0c3f2b4) to head (7c54d31).
Report is 2 commits behind head on 2.17.

Files with missing lines	Patch %	Lines
...on/admin/cluster/health/ClusterHealthResponse.java	64.28%	4 Missing and 1 partial ⚠️
.../opensearch/cluster/health/ClusterIndexHealth.java	95.83%	1 Missing and 2 partials ⚠️
...in/cluster/health/ClusterHealthRequestBuilder.java	0.00%	2 Missing ⚠️
.../opensearch/cluster/health/ClusterShardHealth.java	93.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               2.17   #15799      +/-   ##
============================================
+ Coverage     71.61%   71.62%   +0.01%     
+ Complexity    64505    64491      -14     
============================================
  Files          5264     5264              
  Lines        301860   302016     +156     
  Branches      43942    43966      +24     
============================================
+ Hits         216178   216321     +143     
+ Misses        67637    67625      -12     
- Partials      18045    18070      +25     

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[gbbafna]

Need to get 2.x and main PR merged to get gradle runs running . The 2.x gradle run is not going green . Will retry it