chore(.github/workflows): add PR labels action

[gaius-qi]

Description

This pull request introduces a new GitHub Actions workflow to ensure pull requests are properly labeled. The workflow is designed to enforce the presence of exactly one label from a predefined set.

Workflow Addition:

• .github/workflows/pr-labels.yml: Added a new workflow named "PR Label" that triggers on pull request events (opened, labeled, unlabeled, synchronize). It uses the mheap/github-action-required-labels action to enforce that each pull request has exactly one label from the following set: bug, enhancement, documentation, or dependencies.

Related Issue

Motivation and Context

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 34.30%. Comparing base (50083ff) to head (a1f0235).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3999      +/-   ##
==========================================
- Coverage   34.31%   34.30%   -0.02%     
==========================================
  Files         342      342              
  Lines       40139    40150      +11     
==========================================
- Hits        13775    13772       -3     
- Misses      25454    25468      +14     
  Partials      910      910              

Flag	Coverage Δ
unittests	34.30% <ø> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

see 2 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Liam-Zhao]

LGTM