Directly show the layout selection screen.

When a user clicks on the physical keyboard in order to select a
layout, rather than showing them a dialog with an empty list of
layouts, send them straight to the screen where they can pick which
layouts to enable.

Also, only request keyboard layouts that are appropriate for the
input device we're in the process of configuring.

Bug: 25062009
Change-Id: I4483dfc89afc8d148b2cfa7c6a5f66d2a02f712a