Merge pull request #66973 from fabriziopandini/kubeadm-ha-upgrade

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 ha upgrade

**What this PR does / why we need it**:
This PR implements one of the actions defined by https://github.com/kubernetes/kubeadm/issues/751 (checklist form implementing HA in kubeadm). see [KEP 0015](https://github.com/kubernetes/community/blob/master/keps/sig-cluster-lifecycle/0015-kubeadm-join-master.md) for more context

With this PR, kubeadm implements a new command `kubeadm upgrade node experimental-control-plane` that managed upgrade of control plane components on a secondary control plane instance. 

The entire workflow in case of HA clusters will be:

- Upgrade the control plane
   - run `kubeadm upgrade apply` on a first control plane instance
   - run `kubeadm upgrade node experimental-control-plane` on secondary control plane instances
- Upgrade nodes

**Special notes for your reviewer**:
/CC @timothysc @luxas @chuckha  @kubernetes/sig-cluster-lifecycle-pr-reviews 

**Release note**:
```
kubeadm now has the `kubeadm upgrade node experimental-control-plane` command for upgrading secondary control plane instances created with `kubeadm join --experimental-control-plane`. 
```

docs/.generated_docs

@@ -83,6 +83,7 @@ docs/admin/kubeadm_upgrade_apply.md
 docs/admin/kubeadm_upgrade_diff.md
 docs/admin/kubeadm_upgrade_node.md
 docs/admin/kubeadm_upgrade_node_config.md
+docs/admin/kubeadm_upgrade_node_experimental-control-plane.md
 docs/admin/kubeadm_upgrade_plan.md
 docs/admin/kubeadm_version.md
 docs/admin/kubelet.md
@@ -167,6 +168,7 @@ docs/man/man1/kubeadm-token.1
 docs/man/man1/kubeadm-upgrade-apply.1
 docs/man/man1/kubeadm-upgrade-diff.1
 docs/man/man1/kubeadm-upgrade-node-config.1
+docs/man/man1/kubeadm-upgrade-node-experimental-control-plane.1
 docs/man/man1/kubeadm-upgrade-node.1
 docs/man/man1/kubeadm-upgrade-plan.1
 docs/man/man1/kubeadm-upgrade.1

docs/admin/kubeadm_upgrade_node_experimental-control-plane.md

@@ -0,0 +1,3 @@
+This file is autogenerated, but we've stopped checking such files into the
+repository to reduce the need for rebases. Please run hack/generate-docs.sh to
+populate this file.

docs/man/man1/kubeadm-upgrade-node-experimental-control-plane.1

@@ -0,0 +1,3 @@
+This file is autogenerated, but we've stopped checking such files into the
+repository to reduce the need for rebases. Please run hack/generate-docs.sh to
+populate this file.