[Star Tree] Interfaces Fixes for Star Tree Search

[sarthakaggarwal97]

Description

This change allows the search flows to access StarTreeMetadata so that they can make a decision to cache the query or not based on segment max doc and number of star tree documents.

It also removes the assertion when the child node is not found so that we can gracefully handle the scenarios where we dimension value does not exist in the children.

Related Issues

Resolves #15604

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

❌ Gradle check result for 6c075c1: FAILURE

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[github-actions]

❌ Gradle check result for 4f9dea8: null

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[github-actions]

❌ Gradle check result for 6b67535: FAILURE

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[github-actions]

✅ Gradle check result for bb4d53f: SUCCESS

[github-actions]

❌ Gradle check result for 08722e1: FAILURE

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[github-actions]

❌ Gradle check result for 08722e1: 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 08722e1: UNSTABLE

• TEST FAILURES:

      2 org.opensearch.common.util.concurrent.QueueResizableOpenSearchThreadPoolExecutorTests.classMethod
      1 org.opensearch.common.util.concurrent.QueueResizableOpenSearchThreadPoolExecutorTests.testResizeQueueDown

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

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 71.37%. Comparing base (70ba5a1) to head (08722e1).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
...eindex/datacube/startree/index/StarTreeValues.java	60.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #15603      +/-   ##
============================================
- Coverage     71.90%   71.37%   -0.54%     
+ Complexity    63869    63298     -571     
============================================
  Files          5257     5257              
  Lines        298675   298675              
  Branches      43184    43183       -1     
============================================
- Hits         214775   213178    -1597     
- Misses        66165    67864    +1699     
+ Partials      17735    17633     -102     

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