Update the bouncer to be able to move to either side of a wide screen.

This reverts commit 0f53fd20.

The previous version of this didn't account for padding in onMeasure
(I'd taken this out when copying from FrameLayout, as I didn't think we
used padding), which is applied based on window insets. Tests also added
to check this case.

Forwards we go again :)

Bug: 170858298
Test: Included. Manually tested on phone, with feature enabled too; PIN/Pattern/Password all render correctly.
Change-Id: I7b1f35a185214ffdd2187f1c059f77535197a215