[base-cluster] add self managed gitrepository

[cwrau]

In normal day-to-day usage the user creates the namespace and the resource at the same time.

This is not really working, as flux will refuse to do anything until the namespace exists.

We could create a special gitrepo config, self, which will create 2 gitrepos and kustomizations. One with and one without the cluster.yaml.
This way flux can always reconcile base-cluster and the rest will follow