Automatic merge from submit-queue (batch tested with PRs 49409, 49352, 49266, 48418)
[e2e] Also verify content returned by kube-proxy healthz url
**What this PR does / why we need it**: Enhance kube-proxy url test. This helps to detect the port collision case --- node-problem-detector also serves /healthz to return 200 ok. Verify the content to confirm /healthz is served by kube-proxy.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: From #49263
**Special notes for your reviewer**:
/assign @freehan @nicksardo
**Release note**:
```release-note
NONE
```
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