Automatic merge from submit-queue (batch tested with PRs 41921, 41695, 42139, 42090, 41949)

Rebase kube-proxy and debian-iptables on debian-base

**What this PR does / why we need it**:

Slimmer images are generally preferred, but it's a minor optimization. The larger advantage to this change is the reduced attack surface from removing unnecessary packages, and easier maintenance from sharing a common base image.

Size comparison:
```
gcr.io/google-containers/debian-iptables-amd64:v6         127.9 MB
gcr.io/google-containers/debian-iptables-amd64:v7          45.1 MB
```

**Which issue this PR fixes** https://github.com/kubernetes/kubernetes/issues/40248

**Special notes for your reviewer**:
Tested by deploying to a private test cluster and running the e2es. This will fail the jenkins builds until I push the `gcr.io/google-containers/debian-iptables-amd64:v7` image, which I will do once I have an LGTM.

**Release note**:
```release-note
Clean up the kube-proxy container image by removing unnecessary packages and files.
```

/cc @luxas @ixdy