Update auto-revoke toggle UI w/ hibernation

When hibernation is enabled on S devices, the auto-revoke toggle has
updated text to match with the text in "App Info". In addition, we add a
category title, "Unused apps" to make it clear that the toggle is for
unused apps.

Bug: 191901459
Test: go to app permissions page on apps with/without revocable permissions
Change-Id: Id74a70a2010c96beb50b427ec90b07a18f1bfeb0