Unify the code generation tools in our controllers

[kieron-dev]

Our hack script invokes two scripts:

• vendor/k8s.io/code-generator/generate-groups.sh, which generates
  • the deepcopy functions
  • the versioned client
  • listers
  • informers
• vendor/sigs.k8s.io/controller-tools/cmd/controller-gen, which generates
  • CRDs

Kubebuilder only uses controller-tools. We should follow that example.

Note: this means adopting the controller-runtime client, as we wouldn't be generating the client originally used in eirini. If that's not possible, we can drop this chore.

[gcapizzi]

Before we can work on this story, we'll need to remove all dependencies on the old eirini codebase and the clientset. Blocking for now.