Function: k8scontrol
This function defines a KubeADM and Metal3 control plane, including Cluster, Metal3Cluster, KubeadmControlPlane, and Metal3MachineTemplate resources.
Optional: a versions-airshipctl VariableCatalogue may be used to
override the default Kubernetes version and controlplane disk image.
A base example for this catalogue can be found in the airshipctl-catalogues
function. If using the catalogue, apply the replacements/ entrypoint
at the site level, as a Kubernetes transformer.