add support for adding multiple control plane for multi node

[medyagh]

What Happened?

#17681 (review)

Attach the log file

n/a

Operating System

None

Driver

None

[prezha]

turns out that it'd be easy to "just add" yet another control-plane node to an existing cluster, whereas it's a bit trickier to fully utilise a multi-control-plane (ie, ha) cluster, requiring, amongst other things, a load-balancer for multiple apiservers and quorum for multiple etcd nodes, etc.

also, "upgrading" a non-ha cluster to one that'd become a ha cluster would currently require resetting the cluster, as the kubeadm config would have to change as well, therefore i've created a more general issue #17908 & pr #17909 (containing more details) to address adding native support for creating and managing ha clusters in minikube