Hide "Always" and "Just once" buttons for empty state screens

This change does the following things:
- Groups the button bar and divider in a view with the system
background, so that when they get invisible, the background is not
transparent
- Sets the invisibility of the button bar and divider to invisible
so that the height of the intent resolver is preserved
- Removes the bottom padding for the empty state screen for
the intent resolver to reduce the blank space under it caused
by the now blank button bar

Fixes: 154326163
Test: manual
Change-Id: Iaea4da3f2250f51f9d1d627c1965f42014914084