Apply kp timestamp

[sukhil-suresh]

What? Set a kp timestamp annotation on the resource metatdata on all k8s resource create/patch/update operation initiated by the kp cli.

As part of this effort, have to update the kp import command which currently puts a kpack.io/import-timestamp annotation on all ClusterStacks, ClusterStores and ClusterBuilders during import. Related PR: https://github.com/vmware-tanzu/kpack-cli/pull/47

Annotation to use is kpack.io/kp-timestamp

Why? Even if there is no actual change to a resource when updating/patching, we want to set a kp timestamp annotation annotation on the resource metatdata to force a reconcile. When build/stack/buildpack images are deleted, we want kp commands to heal the resource.