Kubeadm: Expose the `kubeadm join` workflow as phases

- `kubectl debug` gains support for changing container images when copying a pod for debugging, similar to how `kubectl set image` works. See `kubectl help debug` for more information. ([#96058](https://github.com/kubernetes/kubernetes/pull/96058), [@verb](https://github.com/verb)) [SIG CLI]

### Documentation

- Kubeadm: added support for dry running `kubeadm reset`. The new flag `kubeadm reset --dry-run` is similar to the existing flag for `kubeadm init/join/upgrade` and allows you to see what changes would be applied. ([#107512](https://github.com/kubernetes/kubernetes/pull/107512), [@SataQiu](https://github.com/SataQiu))

### Storage

- Kubeadm: when adding new control plane nodes with "kubeadm join", ensure that the etcd member addition is performed only if a given member URL does not already exist in the list of members. Similarly, on "kubeadm reset" only remove an etcd member if its ID exists. ([#127621](https://github.com/kubernetes/kubernetes/pull/127621), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]

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    * - kubeadm upgrade apply supports all standard ways of specifying version via labels. Examples: stable-1.8, latest-1.8, ci/latest-1.9 and similar.
* - kubeadm 1.9 will detect and fail init or join pre-flight checks if kubelet is lower than 1.8.0-alpha ([#52913](https://github.com/kubernetes/kubernetes/pull/52913), [@kad](https://github.com/kad))

- Kubeadm: when adding new control plane nodes with "kubeadm join", ensure that the etcd member addition is performed only if a given member URL does not already exist in the list of members. Similarly, on "kubeadm reset" only remove an etcd member if its ID exists. ([#127620](https://github.com/kubernetes/kubernetes/pull/127620), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]

### Other (Cleanup or Flake)

- Fixes a bug of identifying the correct containerd process. ([#97888](https://github.com/kubernetes/kubernetes/pull/97888), [@pacoxu](https://github.com/pacoxu))
- Fixes add-on manager leader election to use leases instead of endpoints, similar to what kube-controller-manager does in 1.20 ([#98968](https://github.com/kubernetes/kubernetes/pull/98968), [@liggitt](https://github.com/liggitt))

- Ephemeral containers have been added in alpha. These temporary containers can be added to running pods for purposes such as debugging, similar to how `kubectl exec` runs a process in an existing container. Also like `kubectl exec`, no resources are reserved for ephemeral containers and they are not restarted when they exit. Note that container namespace targeting is not yet implemented,...