[Mirror Layers] Added mirrorSurface API to enable mirroring (3/4)

Added a new SurfaceComposer API called mirrorSurface that allows a
client to request a mirror of a particular heirarchy starting from the
passed in layer. The API will return a SurfaceControl that's the parent
of the mirrored layer that can be updated by the client.

Test: MirrorLayerTest
Bug: 131622422
Change-Id: Ia6047f0334eabfc59d6222b2edfd4e9576ba31e5