Add CachingHint into SurfaceFlinger

Some system layers may need to be excluded from surfaceflinger caching
for a variety of reasons, including power or image quality
considerations. This provides a mechanism for those system layers to
never be cached on the GPU.

Bug: 259311918
Test: libcompositionengine_test
Test: run test app and inspect planner state
Change-Id: I35418ad5a41cb2546e3b27b0af290bf3c31a0180