Manage keyguard nav elements using transitions.

Move the logic for managing dimming the navigation bar
elements on the lockscreen into BarTransitions.

Replace search light + camera assets with new
versions at full brightness, and apply 50% dimming
at runtime, including the IME dismiss button.

Remove unused StatusBarManager _NOP hints.

Improve choreography between camera button +
password security (w/ IME).  Fix a few found bugs
in PagedView.

Improve password security unlock transition, manually
fade in back along with the rest of the icons.

Bug:11221659
Change-Id: Ifd1f8c9f400d90542f0ca858b9a4deacabbd518a