fw/b: Button backlight brightness

Squash of:

Author: Ricardo Cerqueira <cyanogenmod@cerqueira.org>
Date:   Fri Nov 23 14:23:16 2012 +0000

    Reintroduce button-backlight (and respective inactivity timeout)

    The power manager rewrite from Change I1d7a52e98f0449f76d70bf421f6a7f245957d1d7
    completely removed support for control of the button backlights, which makes
    all capacitive buttons out there stay dark. The commit message in that change
    mentions it hasn't been implemented _yet_, so this fix should be temporary
    until upstream does their own implementation

    Change-Id: I6094c446e0b8c23f57d30652a3cbd35dee5e821a

Author: Danny Baumann <dannybaumann@web.de>
Date:   Thu Aug 22 08:53:24 2013 +0200

    Add PowerManager integration for button and keyboard backlight.

    Allows setting button and keyboard backlight brightness as well as
    button timeout.

    Change-Id: I550cccafc0a8f90d6347de9261adb26b75955cc4

Author: Steve Kondik <steve@cyngn.com>
Date:   Sat Jan 3 05:13:26 2015 -0800

    power: Disable keyboard/button lights while dozing/dreaming

     * With hardkeys and doze mode enabled, entering suspend results in
       an epic battle over the lights. It's a bad situation. Disable
       them when we're sleepy.

    Change-Id: I7f1fc35a1573717d1ea101a07c4171d6f66d1553

Author: nadlabak <pavel@doshaska.net>
Date:   Sun Jun 7 02:01:05 2015 +0200

    PowerManagerService: Fix updating of mUserActivitySummary

    I7f1fc35a1573717d1ea101a07c4171d6f66d1553 missed the fact that the primary
    purpose of the affected condition block was to update mUserActivitySummary
    and the button/keyboard light handling was just appended to it later.

    This fixes the waking from dream/screensaver by user activity.

    I30c5c8c9c09e3d57ace18cac72b783510b9b3bf3 is removed here as well as it was
    just a band aid.

    jira: NIGHTLIES-1285

    Change-Id: I6b2f6c58e73110787d62e86d4d2ef538638cf491

Author: Bruno Martins <bgcngm@gmail.com>
Date:   Tue Dec 26 17:15:05 2017 +0000

    Forward-port button brightness implementation to O

     * Reworked for the new handler interface, restoring also removed
       methods (partial revert of commit 86c39f9e).

     * Keyboard backlight brightness support left out for now.

    Change-Id: I53f031fa2da394e95a2b29a01eb3c6a8f8132507

Change-Id: I5176a2028c18408c17bac7f25e62b5612fd6c227