Add unit tests for PrioritySorterRestriction class to address JENKINS-69757

[LobsterRavioli]

This pull request introduces unit tests for the PrioritySorterRestriction class to address the issue outlined in JENKINS-69757.
These tests ensure the class functions correctly and handles various scenarios, such as missing ItemInfo and priority range validations.
These tests increase the code coverage of the code-base.

Testing done

• Automated tests were implemented to ensure complete coverage of the PrioritySorterRestriction logic:
  • testCanTake_MissingItemInfo: Verifies behavior when ItemInfo is absent in the QueueItemCache.
  • testCanTake_PriorityRange: Tests canTake behavior for different priority values, validating edge conditions.
  • testGetterMethods: Ensures the correctness of getter methods and that canTake works with Run objects.
    
    

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[MarkEWaite]

Tests look good. Thanks!