SS-28662 Add cvars to support forcing people to departures and making those at depart...

SS-28662 Add cvars to support forcing people to departures and making those at departures invincible (#28765)

* SS-28662 Add cvar to force spawn everyone at departures

This cvar means everyone must spawn at departures. This
could be handy for an admin event? But mostly it's so the
tutorial departures terminal can be seen by all newbies on
gateway servers.

* Small fix to ArrivalsSystem flow

* Remove incorrect todo

* Add godmode arrivals cvar