WallpaperPicker: add a "No Wallpaper" option

This is a squash of the following commits.

Author: Mihai Preda <preda@android.com>
Date:   Sat Jun 11 13:31:55 2011 +0200

    Add a "No wallpaper" wallpaper option.

    The simplest implementation is with a black 1x1px image,
    but it could be implemented in a more efficient way in the future.
    (i.e. the black image is an implementation detail of the
    "no wallpaper" goal).

    On Nexus One (OLED) this "no wallpaper" produces
    45mA current saving compared to the "CM Earth" image wallpaper
    when display is set to max brightness, and 20mA saving on low brightness.

Author: Keith Mok <kmok@cyngn.com>
Date:   Fri May 27 09:49:38 2016 -0700

    Add a set wallpaper button for nowallpaper

    We set the wallpaper to black without a confirm
    button currently and without exit the wallpaper picker.
    This causes odd behaviour.
    Add back a confirm button like live wallpaper picker

    FEIJ-822

Author: Steve Kondik <steve@cyngn.com>
Date:   Thu Oct 13 13:32:03 2016 -0700

    NoWallpaper: Clear lockscreen wallpaper too

Author: Joey Rizzoli <joey@lineageos.org>
Date:   Sat Jan 13 22:34:17 2018 +0200

    NoWallpaper: Add an adaptive icon

Change-Id: Id712314d4e0808145f2180001bfc4dbeea766a46