KafkaSecret Reconciler

The files in this directory were NOT generated via knative.dev/pkg/hack/generate-knative.sh as would normally be expected. This is because we're creating a Controller / Reconciler for the K8S CoreV1 Secret instead of a CRD. We do not want to generate Controllers / Reconcilers for the entire CoreV1 set of resources. Therefore, we've manually copied the previously generated code from the eventing-contrib/kafka' project and modified it for CoreV1 Secrets. This means that whenever the generation of such code is updated we should also perform a manual diff and uplift relevant changes here.