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