MP Infinite Terrain

Checking every update whether the player's camera is about to reveal non-existing terrain would have required constant information about the camera from all players, and is completely redundant which is why the system was turned off in the first place on the switch to MP. Now this is done solely on the server with no bandwidth required by defining server-only trigger-colliders on the edges of the map. Upon collision with any object, the terrain is expanded in that direction, and the collider is pushed towards the new edge.