[CS] Remove CentralSurfaces screen pinning methods.

Instead of having CentralSurfacesCommandQueueCallbacks ->
CentralSurfacesImpl -> NavigationBarController, just have
NavigationBarController listen directly for the screen pinning events.

Bug: 277764509
Test: pin & unpin app with gesture nav -> verify "App pinned" and "App
unpinned" toasts appear
Test: pin & unpin app with 3 button nav -> verify "App pinned" and "App
unpinned" toasts appear
Test: attempt to unpin app -> verify pinning escape toast appear

Change-Id: I8fca0e6fce180c8330d5b782d71ef1a2a916eaa4