update the indexRandom function to create more segments and update IndicesRequestCacheIT, HighlighterSearcherIT to run with minimum of 2 slices (10247)

[neetikasinghal]

Backports #10247

Description

[Describe what this change achieves]

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

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]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/29299/
• CommitID: a134d88
  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]

Compatibility status:

Checks if related components are compatible with change a134d88

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/asynchronous-search.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/neural-search.git]

[sohami]

Looks like a known flaky issue: #10988

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.search.SearchWeightedRoutingIT.testSearchAggregationWithNetworkDisruption_FailOpenEnabled

• URL: https://build.ci.opensearch.org/job/gradle-check/29392/
• CommitID: a134d88
  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 #11009 (a134d88) into 2.x (0f7649f) will decrease coverage by 0.02%.
Report is 9 commits behind head on 2.x.
The diff coverage is 51.61%.

@@             Coverage Diff              @@
##                2.x   #11009      +/-   ##
============================================
- Coverage     70.87%   70.86%   -0.02%     
+ Complexity    58747    58741       -6     
============================================
  Files          4845     4845              
  Lines        277517   277580      +63     
  Branches      40691    40706      +15     
============================================
+ Hits         196687   196701      +14     
+ Misses        64138    64118      -20     
- Partials      16692    16761      +69     

Files	Coverage Δ
...ensearch/action/search/SearchQueryCategorizer.java	96.77% <100.00%> (ø)
...rg/opensearch/common/settings/ClusterSettings.java	92.85% <ø> (ø)
...rg/opensearch/index/translog/RemoteFsTranslog.java	75.35% <100.00%> (-0.26%)	⬇️
...search/index/shard/RemoteStoreRefreshListener.java	84.90% <37.50%> (-1.93%)	⬇️
...in/java/org/opensearch/index/shard/IndexShard.java	68.88% <41.66%> (-0.95%)	⬇️
...arch/index/recovery/RemoteStoreRestoreService.java	12.59% <0.00%> (-0.21%)	⬇️
...java/org/opensearch/index/shard/StoreRecovery.java	55.72% <0.00%> (-1.24%)	⬇️
...arch/gateway/remote/RemoteClusterStateService.java	72.84% <66.66%> (+0.29%)	⬆️

... and 436 files with indirect coverage changes