Some cleanups for window cropping functionality.

At a high level I had two sorts of goals:

1. To remove the weird pinned logic in setSurfaceBoundariesLocked
2. To seperate base crop calculation, and animation exceptions, between
   window state and window state animator.

Itemized changes are as follows:

1. Rename updateSurfaceWindowCrop and calculateSurfaceWindowCrop to
   applyCrop/calculateCrop. It doesn't feel that "SurfaceWindow" was
   adding much.
2. Split screen space and window space (final v non) clip rect
   computation, to make clarity about when each one should be used.
3. Eliminate weird case for pinned stack in setSurfaceBoundaries by
   building it in to calculateFinalClipRect.
4. Extract calculateSystemDecorRect to WindowState as it mostly accesses
   window members.
5. Extract part of calculateCrop to WindowState as
   "calculatePolicyCrop". This was the part that fills mSystemDecorRect.
6. Extract wallpaper animation logic outside of calculatePolicyCrop

Test: bit FrameworksServicesTests:com.android.server.wm.WindowFrameTests
Change-Id: I8ff1dc6ec1206a34994f50ba44d765ab619efbff