power: Add a new power hint for application launches

 * Some devices may prefer a different behavior when launching apps,
   particularly to avoid priority inversion issues. Add support
   for a new LAUNCH_BOOST hint which can be handled in the PowerHAL.

TOMATOL-565

Change-Id: Ie87de6fb3d0a19c134e1b33976571f279a713e52
(cherry picked from commit ad70f850)