Redesigned keyguard layout in the no-SIM case.

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.

(Requires I07bfc0f1c5b3f0e10b8cb72768848251439e19dd)

Bug: 2421380

Change-Id: I46a78c700427d769da6f7f2d3e9f419c2a921a61