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
```