Automatic merge from submit-queue (batch tested with PRs 51733, 51838)
Decouple kube-proxy upgrade/downgrade tests from upgradeTests
**What this PR does / why we need it**:
Fixes the failing kube-proxy migration CI jobs:
- https://k8s-testgrid.appspot.com/sig-network#gci-gce-latest-upgrade-kube-proxy-ds
- https://k8s-testgrid.appspot.com/sig-network#gci-gce-latest-downgrade-kube-proxy-ds
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes#51729
**Special notes for your reviewer**:
/assign @krousey @nicksardo
Could you please take a look post code-freeze (I believe it is fixing things)? Thanks!
**Release note**:
```release-note
NONE
```
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