Expire Metrics

Currently we delete metrics along with application deletion. This is highly inefficient and causes issues like app deletion request timeouts.

Ideally we should never delete metrics explicitly, but rather expire them. That is not trivial however, and requires changing the way we assign IDs to the "things" in CDAP (apps, programs, datasets). Currently, keeping metrics would result in side effects like deploy app with same name of components - it will show metrics from previous app.