Add heuristic slice_size for slice level top buckets in concurrent segment search

[jed326]

Adds a slice_size heuristic for controlling top buckets for terms aggs. See #11584 for more details

Related Issues

Resolves #11584

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

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[jed326]

@reta @sohami would love to hear your thoughts on this PR as well as the problems described in #11584. Thanks!

[github-actions]

Compatibility status:

Checks if related components are compatible with change 67113aa

Incompatible components

Skipped components

Compatible components

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

[github-actions]

❌ Gradle check result for 67113aa: 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?

[reta]

❌ Gradle check result for 67113aa: FAILURE

#11032
#5329

[github-actions]

✅ Gradle check result for 67113aa: SUCCESS

[sohami]

@jed326 We should also have a document change for this to explain about slice_size heuristics in concurrent search flow. Users can use shard_size parameter itself to control the number of buckets considered at each slice level to get correct doc count per bucket on a shard. Good thing about this is If shard_size is chosen correctly then this default heuristic should work fine out of the box.