Automatic merge from submit-queue (batch tested with PRs 55988, 53555, 55858). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Add IPv6 and negative UT test cases for proxier's deleteEndpointConnections

This change adds IPv6 and negative UT test cases for the proxier's deleteEndpointConnections.

Changes include:
- Add IPv6 UT test cases to TestDeleteEndpointConnections.
- Add negative UT test case to TestDeleteEndpointConnections for
  handling case where no connections need clearing (benign error).
- Add negative UT test case to test unexpected error.
- Reorganize UT in TestDeleteEndpointConnections so that the fake
  command executor's command and scripted responses are generated on
  the fly based on the test case table (rather than using a fixed
  set of commands/responses that will need to be updated every time
  test cases are added/deleted).
- Create the proxier service map in real time, based on the test case
  table (rather than using a fixed service map that will need to be updated
  every time test cases are added/deleted).

fixes #53554



**What this PR does / why we need it**:
This change adds IPv6 and negative UT test cases for the proxier's
deleteEndpointConnections.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #53554

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```