Add loaders to DrawerFragment and make status bar transparent

- This CL addresses a TODO to load groups and filters from
  DrawerFragment directly.
- Also, avoiding adding fragments to FragmentManager of a
  Fragment works around a crash on LMP.
- Wrap RecyclerView with a FrameLayout to go full screen
  with a ScrimDrawable

Bug: 34062530

Test: add and remove accounts and observe changes in side nav

Change-Id: I63943a9d596aa32301609d6ab1b9d49c0c784356