tuna: add health HAL
Placeholder example health how for now, preserves default actions with no
additional logic.
overlay: enable multiuser.
overlay: don't use SRC optimization on tuna.

"Whether we should use SRC drawing mode when drawing the scrim behind. If this flag is set, we change the canvas opacity so libhwui doesn't call glClear on our surface, and then we  draw the scrim with SRC to overwrite the whole buffer, which saves us a layer of overdraw.  However, SRC performs poorly on some devices, where it is more efficient to glClear + SRC_OVER, in which case this flag should be disabled.
overlay: disable textview fades
tuna: add Healthd changes.
revert:overlay: enable multiuser.

THE LAG IS STRONG WITH THIS ONE