Implement Phase 3 of per-display power states

In this phase a DisplayPowerController is created per-display. However
each display is still controlled by the default display's
DisplayPowerController.

Bug: 138328918
Test: manual - Boot device and toggle display power
Change-Id: I4c608d1e18476a87d2da4bc1c120d62c39db25eb
3 files changed