assist: Fix reported colors/styles for TextView/Switch

Changes to the data provided to AssistStructure:
* Text foreground color is correct even if the view has not yet been
painted.
* Text background color is now always 1 (TEXT_COLOR_UNDEFINED) for a
TextView, as it has no separate concept of background color.
* Switch now reports the text size/color/style of the label text
(usually user visible) rather than the on/off text on the button
itself (usually hidden in Material, and not usually revelant when
visible).

Bug: 21080375
Change-Id: I7e15f68d89510a76cab76031c2c8ca6ca3f32435