fix: do not allow scaling down controlplane to zero

[Unix4ever]

Doing that is pretty pointless as it's going to destroy a cluster. Instead of doing that cluster should be deleted and recreated.

And with the new approach without init nodes scaling cluster back up won't be able to succeed as bootstrap is done only a single time.

Still allowing user to set replicas to zero, but block scaling in the controller with error messages when there's only a single node remaining.

Signed-off-by: Artem Chernyshev artem.chernyshev@talos-systems.com

[Unix4ever]

/approve

[Unix4ever]

/m --ff