Automatic merge from submit-queue (batch tested with PRs 58540, 62314). 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>.
Add ability to specify port for kubeadm `API.ControlPlaneEndpoint`
**What this PR does / why we need it**:
When `API.ControlPlaneEndpoint` is used, the `BindPort` of the
apiserver is currently assumed, which means a load balancer cannot
listen on a different port than the apiserver. This extends the
`ControlPlaneEndpoint` to take an optional port which may differ
from the apiserver's `BindPort`.
**Release note**:
```release-note
The kubeadm config option `API.ControlPlaneEndpoint` has been extended to take an optional port which may differ from the apiserver's bind port.
```
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