- Previously it only enforced whether an app could enter PiP as it was
hiding.
- Also updating metrics constant name to reflect the change.
- Adding public OPSTR for apps to check if it the user has disabled PiP
Bug: 35957404
Test: android.server.cts.ActivityManagerPinnedStackTests
Change-Id: I979b5c6d4c85946623999ced1cfb197d830ccecb