[Backport 2.x] Star tree index validations (#15533)

[bharath-techie]

---

Description

Backport of #15533

Related Issues

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

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 6c5c5af: 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 2946fa4: 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?

[bharath-techie]

#13846 flaky test

[github-actions]

❌ Gradle check result for c040b41: 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 4cfeff7: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 79.31034% with 18 lines in your changes missing coverage. Please review.

Project coverage is 71.67%. Comparing base (62e943c) to head (4cfeff7).
Report is 15 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
...va/org/opensearch/index/mapper/StarTreeMapper.java	70.27%	9 Missing and 2 partials ⚠️
...java/org/opensearch/index/mapper/ObjectMapper.java	0.00%	3 Missing and 1 partial ⚠️
...h/cluster/metadata/MetadataCreateIndexService.java	86.95%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #15610      +/-   ##
============================================
- Coverage     71.68%   71.67%   -0.01%     
+ Complexity    64023    64022       -1     
============================================
  Files          5243     5243              
  Lines        299319   299404      +85     
  Branches      43568    43584      +16     
============================================
+ Hits         214566   214611      +45     
+ Misses        66820    66798      -22     
- Partials      17933    17995      +62     

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