Make IndexStoreListener a pluggable interface

[jed326]

Description

I have a use case where I have a custom file cache implementation and in order to not have dangling entries in my fc I need to implement IndexStoreListener to clean up my file cache when shards move off a node. Today that is not possible as IndexStoreListener is an @opensearch.internal interface and not pluggable, which this PR changes.

Long term I think the solution is to make the FileCache itself pluggable, but that is much more complicated and anyways would require us to expose this interface as pluggable, so I believe this is a useful intermediary step.

The other thing to note is in Node.java I am now creating the CompositeIndexStoreListener regardless of if it isSearchNode() or not as it should be up to the specific listener implementations to determine how/when to perform their action.

Check List

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

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[jed326]

@andrross @bugmakerrrrrr @sohami could you review this PR as it is related to #11443?

[github-actions]

❌ Gradle check result for 8c4fd86: FAILURE

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[github-actions]

❌ Gradle check result for ceeb08a: FAILURE

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❌ Gradle check result for 65497a0: FAILURE

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[github-actions]

✅ Gradle check result for 2de2403: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 72.11%. Comparing base (034bd2b) to head (ca32a2f).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...org/opensearch/index/store/IndexStoreListener.java	80.95%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #16583      +/-   ##
============================================
+ Coverage     72.04%   72.11%   +0.07%     
- Complexity    65093    65102       +9     
============================================
  Files          5314     5315       +1     
  Lines        303541   303572      +31     
  Branches      43921    43925       +4     
============================================
+ Hits         218683   218935     +252     
+ Misses        66946    66672     -274     
- Partials      17912    17965      +53     

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[sohami]

lgtm. Will wait for others to approve as well

[bugmakerrrrrr]

LGTM

[andrross]

Looks good, once the @PublicApi tag is added per @reta's comment

[github-actions]

❕ Gradle check result for ca32a2f: UNSTABLE

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.