Use UUID instead of IP address for tracking agent (#4470)

[sjberman]

Cherrypick of #4470

Problem: In some cases, a Pod's IP address may not actually be the IP of the Pod. It could be the IP of the node it's running on. This makes verification and tracking difficult to impossible.

Solution: Use the UUID of the container instead of the IP address, and loosen the validation to not care about the address that connects to the control plane.

Also needed to fix the agent's ability to identify us as a container, because otherwise the UUId was of the node, not the container. This involved reverting a previous fix that was added after removing the default service account directory, which agent looked for.

Testing: Verified that everything still works when not using the IP address as the key.

Checklist

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• 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.

Fix issue where agent's Pod IP cannot be used to track the connecting data plane Pod

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.22%. Comparing base (89aee48) to head (aef57a6).
⚠️ Report is 1 commits behind head on release-2.3.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-2.3    #4472      +/-   ##
===============================================
- Coverage        86.24%   86.22%   -0.02%     
===============================================
  Files              132      132              
  Lines            14566    14557       -9     
  Branches            35       35              
===============================================
- Hits             12562    12552      -10     
- Misses            1791     1792       +1     
  Partials           213      213              

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