Fix delete index template failed when the index template matches a data stream but is unused

[gaobinlong]

Description

Index templates without a explicit data_stream attribute cannot be used by data stream actually, but when deleting an ordinary index template which is not used by any data stream, if the index patterns match a data stream, then the delete operation fails with an exception unable to remove composable templates [test] as they are in use by a data streams [test]. This PR fixes the bug and add some test code.

Related Issues

Resolves #9194

Check List

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

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❌ Gradle check result for 7e47732: FAILURE

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❌ Gradle check result for 1212877: FAILURE

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[gaobinlong]

@reta @dblock @andrross could you help to review this PR, thank you!

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❌ Gradle check result for 1212877: FAILURE

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❌ Gradle check result for 3dea93d: FAILURE

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❌ Gradle check result for 3dea93d: FAILURE

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❌ Gradle check result for 3dea93d: FAILURE

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❌ Gradle check result for 3dea93d: FAILURE

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❌ Gradle check result for 1c0bd1c: FAILURE

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❕ Gradle check result for f092892: UNSTABLE

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 71.88%. Comparing base (48634bd) to head (f092892).
Report is 3 commits behind head on main.

Files	Patch %	Lines
...cluster/metadata/MetadataIndexTemplateService.java	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #15080      +/-   ##
============================================
+ Coverage     71.82%   71.88%   +0.05%     
- Complexity    62778    62818      +40     
============================================
  Files          5169     5169              
  Lines        294646   294665      +19     
  Branches      42610    42616       +6     
============================================
+ Hits         211644   211834     +190     
+ Misses        65573    65419     -154     
+ Partials      17429    17412      -17     

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