Update picture-in-picture settings to match mocks.

- Removing switches in top-level picture-in-picture settings, adding
  details screen for each app which contains the switch and some
  additional information.

Bug: 35957404
Test: make -j40 RunSettingsRoboTests
Change-Id: Ib22df8a52ab857e071ec43dd3e5d1f5282db35cb