Automatic merge from submit-queue (batch tested with PRs 46458, 50934, 50766, 50970, 47698)
kubeadm: Make the self-hosting with certificates in Secrets mode work again
**What this PR does / why we need it**:
This PR:
- makes the self-hosting with certificates in Secrets mode work
- makes the wait functions timeoutable
- fixes a race condition where the kubelet may be slow to remove the Static Pod
- cleans up some of the self-hosting logic
- makes self-hosting-with-secrets respect the feature flag
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
fixes: https://github.com/kubernetes/kubeadm/issues/405
**Special notes for your reviewer**:
This is work in progress. I'll add unit tests, rebase upon https://github.com/kubernetes/kubernetes/pull/50762 and maybe split out some of the functionatlity here into a separate PR
**Release note**:
```release-note
NONE
```
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