Prepare LightBarController for multi display

1 - Split interface and impl
2 - Turn impl into an @AssistedInject class
3 - Add a stop() method to impl, so that things can be unregistered
4 - Create a PerDisplayStore for it

NavigationBar was already creating an instance per display, therefore
their code is already using the new store. This ensures everyone is
using the same instance per display.

Test: NavigationBarTest.java
Test: LightBarControllerTest.java
Test: LightBarControllerStoreImplTest.kt
Flag: EXEMPT no behavior change. NavigationBar was already creating one
      instance per display. StatusBar continues to use the default
      instance as before.
Bug: 369337696
Change-Id: I988b220d92811ef72c4011638a2641163d65e089