Make the keyguard pattern view shrink when the device is half open.

This is done by converting it to use a ConstraintLayout. This allows us
to set a guideline based on the screen percentage to size the pattern
view. After doing that, we can resize the entry method in much the same
was as we do it for the PIN pad.

Note: this CL also moves the pattern view unconditionally to the bottom
of the screen. This is by design; the new UX designs anchor all keyguard
input methods to the bottom of the screen instead.

Bug: 191347942
Test: Manually tested.
Change-Id: I1b53cad22ae4d2c7d738c2b48110283f53aa2e68