Automatic merge from submit-queue (batch tested with PRs 47435, 46044)
kubeadm: Make self-hosting work and split it out to a phase
**What this PR does / why we need it**:
- Removes the old self-hosting code
- Puts the new self-hosting code in `phases/selfhosting`
- The new code reads manifests from disk (static pods)...
- ...mutates the PodSpec as necessary...
- ...and posts the DaemonSet to the API Server...
- ...and waits for it to come up
- Uses DaemonSets for all control plane components
- Creates a `kubeadm alpha phase selfhosting` command that can be invoked against any kubeadm-cluster after install.
**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/127
(large part of at least)
**Special notes for your reviewer**:
Please only review the fourth commit, based on https://github.com/kubernetes/kubernetes/pull/47345
**Release note**:
```release-note
kubeadm: Make self-hosting work by using DaemonSets and split it out to a phase that can be invoked via the CLI
```
@kubernetes/sig-cluster-lifecycle-pr-reviews @jbeda
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