Add a workflow that requests review from @tailscale/k8s-devs on PRs
touching Kubernetes operator, kube libraries, container build, etc.
Also cleans up check out code on k8s and dataplane workflow.
Updates #cleanup
Change-Id: I6fd7cacf71e1299f7e8f546ef52c4063fbf6bab8
Signed-off-by: Fernando Serboncini <fserb@tailscale.com>