power: Add CPU boosting interface

 * Boosts CPU using Power HAL for the given duration.
 * Duration is given in microseconds.
 * Power HAL must implement POWER_HINT_CPU_BOOST.

Change-Id: Ic79baf7e3d0f75483c2fe8a242b4c3d93368b68b

Add CPU boosting hooks

 * Send boost hint during scrolling
 * Still relevant on even high-end hardware

Change-Id: I72f2c2851b01fbceabddead03a4c3a7a0526ca61

perf: Send a boost hint when a key on the navbar is pressed

 * A lot of stuff happens, especially when invoking recents.
 * Get ahead of the storm by sending a boost hint before
   kicking off the animations.

Change-Id: I0cecd0c58f8bc8479ea44f63af796500d7b9d7d2

perf: Send boost hint during initial launch

Change-Id: I26afc909c35e514958894b0a07a650a20ce6e537