Modify SurfaceView to use SurfaceFlinger child surfaces.

Here we have SurfaceView bypass the WindowManager and speak
directly to SurfaceFlinger using child surfaces. We also
implement some logic in the WM to handle child surfaces
in various Surface replacement scenarios.

Bug: 28858420
Bug: 31518219
Bug: 34888808
Bug: 35588318
Bug: 35396882
Test: Existing tests still pass (except for the ones that don't and will be deleted).
Change-Id: Icb7259365b51ebe8c7f6c7cd4f9ba29f9fce08a4