Autofill: new UX for TV and support themes

1. Define default Themes for autofill window and save dialog.
   (http://go/theme_autofill). Phone uses light themes, TV uses
   dark themes.
2. Apply autofill theme to RemoteViews passed from autofill service.
   So this can make sure the textColor of RemoteViews matches
   the background of autofill theme uses.
   Updated public javadoc that autofill service should not
   hardcode color values.
3. A new TV ux that occupies half screen height (go/autofill-for-tv).
   TV autofill now passes unhandled physical keyevent to app window
   in the same way phone/tablet does.
4. Fixed ATV autofill window to be SYSTEM_DIALOG, so it wont be
   clipped by app activity window (DialogLauncherActivityTest).

Bug: 71720680
Bug: 74072921
Test: CtsAutofillTest

Change-Id: Ib570227b0958b1800e8f0600b8aec36478568d74