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I confirmed with the original author here that this view is obsolete.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: I6c7c0658d9f0f47e8c69f1170d68ad1bb77f221f