Add CEL validation test for timeout in ClientSettingsPolicy

[shaun-nx]

Proposed changes

Add tests for CEL validation test for timeout in ClientSettingsPolicy

Resolves timeout CEL validation requirement of #3621

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.15%. Comparing base (1dd7381) to head (df8541b).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3695      +/-   ##
==========================================
- Coverage   87.16%   87.15%   -0.01%     
==========================================
  Files         128      128              
  Lines       15779    15779              
  Branches       62       62              
==========================================
- Hits        13753    13752       -1     
- Misses       1866     1867       +1     
  Partials      160      160              

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[bjee19]

lgtm