CP/DP Split: handle kill signal

[sjberman]

Problem: The data plane container was not properly handling the kill signal when the Pod was Terminated.

Solution: Update the entrypoint to catch the proper signals.

Testing: Verified that the Pod is terminated immediately instead of hanging.

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

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.79%. Comparing base (6337c97) to head (12242aa).
Report is 184 commits behind head on change/control-data-plane-split.

Additional details and impacted files

@@                         Coverage Diff                         @@
##           change/control-data-plane-split    #3260      +/-   ##
===================================================================
- Coverage                            89.74%   86.79%   -2.96%     
===================================================================
  Files                                  109      124      +15     
  Lines                                11150    14292    +3142     
  Branches                                50       62      +12     
===================================================================
+ Hits                                 10007    12405    +2398     
- Misses                                1083     1751     +668     
- Partials                                60      136      +76     

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