Add rotary support to the nofitication shade.

- Add a FocusArea
- Add a FocusParkingView

The FocusArea's main contribution in this case is to
allow OEM customizability of the focus highlight for
the rotary feature. The UI was already in a rotary
compatible state without it (i.e. I could navigate
around even before adding this change)

BUG: 157937087
Test: manual
Change-Id: If02f9e73ca3a941fc783a63924135a2f78b12723