SF: Move postFrameBuffer to CompositionEngine

This moves SurfaceFlinger::postFrameBuffer to
compositionengine::Output::postFrameBuffer, with some implementation
details in compositionengine::Display::presentAndGetFrameFences.

Test: atest libsurfaceflinger_unittest libcompositionengine_test
Test: atest CtsColorModeTestCases
Test: atest CtsDisplayTestCases
Test: atest CtsGraphicsTestCases
Test: atest CtsUiRenderingTestCases
Test: atest CtsViewTestCases
Test: atest android.media.cts.EncodeVirtualDisplayWithCompositionTest
Bug: 121291683

Change-Id: I8cda7bf26ec4b9e437c91ef951c5030f8d2752e9