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 87.00%. Comparing base (6337c97) to head (c123a4b).
Report is 182 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%   87.00%   -2.75%     
===================================================================
  Files                                  109      121      +12     
  Lines                                11150    13739    +2589     
  Branches                                50       62      +12     
===================================================================
+ Hits                                 10007    11953    +1946     
- Misses                                1083     1668     +585     
- Partials                                60      118      +58     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.