Added adb commands to set and reset brightness.

adb shell cmd display set-brightness BRIGHTNESS command sets the
screen brightness programatically.
adb shell cmd display reset-brightness resets the brightness
configuration to the default configuration.

Test: run "adb shell cmd display set-brightness <number>" and watch
      the magic happen.

Test: run "adb shell cmd jobscheduler run -f
      com.google.android.apps.turbo 104" to push a new configuration,
      then run "adb shell cmd display reset-brightness-configuration"
      to reset it. If it's not noticable enough, you can manually
      edit /data/system/display-manager-state.xml: for example, set
      nits="0.0" for all the <brightness-point />s in the
      <brightness-curve /> to make it as dark as posible.

Fixes: 77574628

Change-Id: I37e19c1e662370e60c9f616a3710780f16418620