SF: Move DisplaySurface into CompositionEngine

The CompositionEngine now provides the interface for a DisplaySurface.

For the moment SurfaceFlinger still provides implementations, but those
may be moved into CompositionEngine too.

Test: atest libsurfaceflinger_unittest libcompositionengine_test
Bug: 121291683
Change-Id: I446e57952d59abc137b3b23203b2e093f6262ef3
16 files changed