Automatic merge from submit-queue
kubeadm: Move some code from apiclient.go to the dedicated apiconfig phase
**What this PR does / why we need it**:
Add constants and somewhat refactor the RBAC code as well + some cleanup.
I'm planning to rewrite the code in `setupmaster.go` later, but this PR has only the move of the code for easier reviewing.
**Special notes for your reviewer**:
This is broken out from: https://github.com/kubernetes/kubernetes/pull/40556
**Release note**:
```release-note
NONE
```
@mikedanese @pires @dmmcquay @dgoodwin
582187b6fb