Remove KeyguardHostView

I confirmed with the original author here that this view is obsolete.
I'm reducing complexity by moving any logic added here to
keyguardsecuritycontainercontroller.

Bug: 267821080
Test: test sim screen
Test: show/hide bouncer scrimmed and not scrimmed
Test: Unit tests

Change-Id: I63207fa25bbef0121e61b200c6a5646e7362fb33