kapp-controller should have a ClusterAPI story

I love how kapp-controller brings the declarative model of consistent k8s workloads to everyday operations (i.e. "Install version x.y.z of FluentBit on all my k8s clusters).

I think if it is combined with ClusterAPI, there is a very compelling story. In the same way that I can define a source of truth for my kubernetes workloads, I can define a source of truth for my kubernetes _landscape_ (e.g. "dev", "test", "prod" k8s clusters).

If kapp-controller deals with managing "packages", and a "package" is really a set of manifests, and if a Kubernetes cluster can be expressed in a manifest, then kapp-controller can treat a kubernetes cluster as just another package. This would be a great hook for people working toward a "gitops" model and unlocks a lot of use cases (fully-automated deployments, edge k8s clusters, rapid infra iteration, etc...)