Automatic merge from submit-queue (batch tested with PRs 37270, 38309, 37568, 34554)

kubeadm UX improvements for the v1.5 stable release

This PR targets the next stable kubeadm release.

It's work in progress, but please comment on it and review, since there are many changes.

I tried to group the commits logically, so you can review them separately.

Q: Why this large PR? Why not many small?
A: Because of the Submit Queue and the time it takes.

PTAL @kubernetes/sig-cluster-lifecycle

_Edit:_ This work was splitted up in three PRs in total