Automatic merge from submit-queue. 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>.

 kubeadm: Remove the `.CloudProvider` and `.PrivilegedPods` configuration option

**What this PR does / why we need it**:
Removes the `.CloudProvider` option, it has been experimental for a long time. People should now use external cloud providers, which is beta in v1.11. Most importantly, you can get the exact same behavior in the API by utilizing the `.*ExtraArgs` and `.*ExtraVolumes` fields.
Removes `.PrivilegedPods` as that serves a super small edge case with the legacy cloud provider, and only for openstack.

**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**:
Depends on PRs:
 - [x] #63799
 - [x] #63788

**Release note**:

```release-note
[action required] In the new v1alpha2 kubeadm Configuration API, the `.CloudProvider` and `.PrivilegedPods` fields don't exist anymore.
Instead, you should use the out-of-tree cloud provider implementations which are beta in v1.11.
If you have to use the legacy in-tree cloud providers, you can rearrange your config like the example below.
If you need to use the `.PrivilegedPods` functionality, you can still edit the manifests in
`/etc/kubernetes/manifests/`, and set `.SecurityContext.Privileged=true` for the apiserver
and controller manager.
---
kind: MasterConfiguration
apiVersion: kubeadm.k8s.io/v1alpha2
apiServerExtraArgs:
  cloud-provider: "{cloud}"
  cloud-config: "{path}"
apiServerExtraVolumes:
- name: cloud
  hostPath: "{path}"
  mountPath: "{path}"
controllerManagerExtraArgs:
  cloud-provider: "{cloud}"
  cloud-config: "{path}"
controllerManagerExtraVolumes:
- name: cloud
  hostPath: "{path}"
  mountPath: "{path}"
---
```
@kubernetes/sig-cluster-lifecycle-pr-reviews @dims @liztio