WaitForAllControlPlaneComponents is a new feature gate
that can be used to tell kubeadm to wait for all control plane
components and not only kube-apiserver.
- Add the Waiter function WaitForControlPlaneComponents
that waits for all CP components in parallel. Uses the regular
healthz endpoint for checks of status 200.
- Add a new experimental phase to kubeadm join called "wait-control-plane".
A similar phase exists for kubeadm init.
