[flexiglass] Bouncer throttling - view models.

View model logic for throttling input entry on the
bouncer when the user enters wrong input too many times.

Bug: 280877228
Test: unit tests
Test: manually verified in PIN, pattern, and password that entering the
wrong input 5, 10, 15, or any number above 15, times shows the
throttling dialog.
Test: manually verified that the throttling dialog cannot be dismissed
without touching its "Ok" button (tapping outside or hitting back don't
dismiss it)
Test: manually verified that input on the bouncer is disabled as the
message is showing the countdown for 30 seconds.
Test: manually verified that after the 30 second countdown, the input
is enabled again and entering the correct input unlocks Flexiglass.

Change-Id: I59146f66ab1fce82fbbe9b8ed56699157ae35267