lineage-sdk: DnD light brightness control for battery and notifications

*) Support separate normal and dnd led brightness levels for battery
   and notifications.

*) Move lineage-specific notification bundle extras definitions from fw/b
   to LineageNotification here in the sdk.

*) In addition to the existing bundle extra EXTRA_FORCE_SHOW_LIGHTS, add
   a new extra EXTRA_FORCE_LIGHT_BRIGHTNESS that can be used to override
   the brightness level set by a Lineage system setting brightness level
   on a per notification basis.  This is used by the brightness sliders
   in LineageParts that otherwise would have to juggle changing / restoring
   the system led brightness setting whenever the a slider is on display.

*) Disable all lights in dnd mode when lineage setting ZEN_ALLOW_LIGHTS
   is set to 0.

Change-Id: I917f402a291682b582f68c8324a33c461357dad9