Fix responsibility check for existing shards allocator when timed out

[imRishN]

Description

With #14848, we introduced capability to make reroute iteration time-bound. Currently OpenSearch uses two primary allocators - ExistingShardsAllocator which is responsible for allocating existing shards, and BalancedShardsAllocator which handles the allocation of all unassigned shards.

This PR adds responsibility check in ExistingShardsAllocator such that newly created shards are not added to ignored list.

Related Issues

Resolves #15222

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 f75154d: ABORTED

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 fa0ad4e: SUCCESS

[github-actions]

❌ Gradle check result for 474060e: 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 4e8ee65: SUCCESS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.94%. Comparing base (b6c80b1) to head (4e8ee65).
Report is 3 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #15223      +/-   ##
============================================
+ Coverage     71.90%   71.94%   +0.03%     
- Complexity    63033    63086      +53     
============================================
  Files          5197     5197              
  Lines        295313   295315       +2     
  Branches      42677    42678       +1     
============================================
+ Hits         212354   212457     +103     
+ Misses        65552    65462      -90     
+ Partials      17407    17396      -11     

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[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/OpenSearch/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.x
# Create a new branch
git switch --create backport/backport-15223-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 625dd5a3bcd1a56d07f49492225413eae5db58fb
# Push it to GitHub
git push --set-upstream origin backport/backport-15223-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-15223-to-2.x.