For accessibilty settings, both on the main page
and the shortcut picker.
Also now observing settings that could be toggled
by the shortcut, so changes can be reflected immediately
in the settings ui.
Bug: 34621067
Fixes: 70335904
Test: Observe icons in settings and shortcut picker.
Toggling color inversion and color correction now changes
the setting ui immediately.
Change-Id: Id27b6471376059288ff971e5aea72d76078bef36
