Automatic merge from submit-queue (batch tested with PRs 50872, 51103, 51220, 51285, 50841)

kubeadm: Add 'kubeadm upgrade plan' and 'kubeadm upgrade apply' CLI commands

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

This PR is splitted out from: https://github.com/kubernetes/kubernetes/pull/48899 and only handles the CLI/command code. It adds no-op functions only to `phases/upgrade`.

A large chunk of this code is unit tests.
The code here should be pretty straightforward as there is no actual upgrade or business logic here.
It would be cool to get this merged soon-ish.

**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/14

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```
@kubernetes/sig-cluster-lifecycle-pr-reviews PTAL