Automatic merge from submit-queue (batch tested with PRs 63272, 63782, 63715, 63811, 63803). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Stop installing kubeadm types in the generic, legacy scheme

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

Right now the kubeadm API types are (wrongly from a correctness perspective) installed in the "catch-all" and now legacy `pkg/api/legacyscheme`. Instead, we should use our own, kubeadm-specific `scheme` where our API types are registered. Doing this also cuts one dependency on the internal core API types.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Part of https://github.com/kubernetes/community/pull/2131

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```
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