Replace many references to NPVC with an interface

Replaces all but 1 reference to NPVC with ShadeViewController and
the CentralSurfacesImpl reference with the larger ShadeSurface
interface. Fixes a small number of oversights from the CL that
created the interfaces, i.e. adding/moving methods and constants.

Test: manually ran through go/shade-cujs
Test: atest SystemUITests SystemUIGoogleTests
Bug: 273789810
Change-Id: I6f5cc38e0385939872394111be39912dd403d50d