Redesigned keyguard layout in the no-SIM case. DO NOT MERGE

The emergency call button has been removed (since the user
can disable the keyguard, open the phone app, and enter the
emergency number there).

This change also restores a number of the informational &
help messages that were previously removed from the lock
screen.

Bug: 2421380
Change-Id: I4dda16be5d54c1e0ab4e26914c63d1f5b922cfe8