Fix unassigned shard allocation for batch mode

[SwethaGuptha]

Description

This change fixes issues shard allocation in batch batch. Changes in the PR :

1. Move decision evaluation and execution of decision together for each unassigned shard of a batch to ensure the cluster state is updated before we make decision for another shards
2. In-order to correctly handle cases where shards have multiple unassigned replicas, evaluation and decisions execution will be done for all replica shards of a shard if the shard is part of the batch that needs to be allocated. This is required as our batches will contain only one entry per shard id.

Related Issues

Resolves #13702, #13962

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• API changes companion pull request created.
• 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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[github-actions]

❌ Gradle check result for c0aa1f6: 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 828b854: FAILURE

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[github-actions]

❌ Gradle check result for 828b854: 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?

[codecov]

Codecov Report

Attention: Patch coverage is 82.75862% with 10 lines in your changes missing coverage. Please review.

Project coverage is 72.14%. Comparing base (b15cb0c) to head (48f3402).
Report is 410 commits behind head on main.

Files	Patch %	Lines
...opensearch/gateway/PrimaryShardBatchAllocator.java	76.19%	2 Missing and 3 partials ⚠️
...opensearch/gateway/ReplicaShardBatchAllocator.java	86.48%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13748      +/-   ##
============================================
+ Coverage     71.42%   72.14%   +0.71%     
- Complexity    59978    62407    +2429     
============================================
  Files          4985     5117     +132     
  Lines        282275   291684    +9409     
  Branches      40946    42167    +1221     
============================================
+ Hits         201603   210421    +8818     
- Misses        63999    64186     +187     
- Partials      16673    17077     +404     

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[github-actions]

✅ Gradle check result for 48f3402: SUCCESS