Fix Activity leaks

* Workspace and WallpaperSurfaceCallback's cleanUp was not being called,
leaking listeners and preventing surfaces to be properly disposed of

* Moved to use ApplicationContext in Injector where possible

* Fixed lambdas in Injector that were keeping a reference to the Context

Test: ran profiler, switched wallpapers via quick-switch, colors, manually
set live wallpapers, clocks, and changed affordances
Bug: 285978251

Change-Id: I8396761c09596c7da0603fb97596336dbd36e929