SF: Defer setDisplayBrightness to Binder thread

setDisplayBrightness blocks for a long time so cannot run on the main
thread. Keep display lookup on the main thread, but return a deferred
future to the Binder thread and run it there.

Bug: 154202427
Bug: 123715322
Test: systrace with backdoor to set brightness
Change-Id: I88e60c95db5fdcaa1bf5ebb9711e3bf5ab6539a1
7 files changed