Implement GKI timers based on wake alarms and wake locks.

Implement GKI timers based on wake alarms and wake locks.

Before this change, bluedroid was unable to acquire wake locks
because the Bluetooth process didn't have permissions to write to
/sys/power/wake_*. We are now making wake locks accessible to
bluedroid through a HAL callout back into Java code.

The previous design did not use wake alarms. Bluedroid would attempt
to hold a wake lock until all pending timers expired, which is awful
if a timer is scheduled seconds or minutes from now. There is a
15min timer in bluedroid now so holding a wake lock for the entire
duration of pending alarms is unacceptable (power cost). The new
implementation uses a hybrid approach: if the next deadline is < 3s
away, we take a wake lock. If it is further than 3s away, we set a
wake alarm and release the wake lock.

As a result of this change, we have also eliminated a thread whose
sole purpose was to wake up every 10ms and update timers.

Change-Id: I46cd4edfcad2f5dce23c4003a14a617e7bf00541