Add metadata for mouse cursor.

Mouse cursor metadata is stored in a parcel with a int32_t for mouse
cursor type, and two floats for mouse hotspotX/Y. Therefore move the
parcel to byte vector conversion into SurfaceComposerClient. If anyone
needs to store metadata in raw byte vector we can change the interface
later.

Bug: 130822623
Test: SurfaceFlinger can get cursor type and hotspot.
Change-Id: Ia7e0c952fcaefd14280322d9b2269f4dba38e8da
Merged-In: Ia7e0c952fcaefd14280322d9b2269f4dba38e8da