[Backport 2.x] Change priority for scheduling reroute during timeout (#16445)

[imRishN]

Description

Backport #16445

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 e64f25c: null

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 67e973a: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 88.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 71.99%. Comparing base (87b4b91) to head (67e973a).
Report is 1 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
.../allocation/allocator/BalancedShardsAllocator.java	78.57%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #17622      +/-   ##
============================================
- Coverage     72.02%   71.99%   -0.03%     
+ Complexity    66032    65967      -65     
============================================
  Files          5342     5342              
  Lines        307289   307313      +24     
  Branches      44848    44850       +2     
============================================
- Hits         221316   221246      -70     
- Misses        67505    67574      +69     
- Partials      18468    18493      +25     

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