Refactor the Tile to a full Atlas

This atlas is a set of chunks and supports resizing

pkg/game/world.go

@@ -32,6 +32,7 @@ func NewWorld() *World {
 	return &World{
 		Rovers:       make(map[uuid.UUID]Rover),
 		CommandQueue: make(map[uuid.UUID]CommandStream),
+		Atlas:        NewAtlas(2, 10), // TODO: Choose an appropriate world size
 	}
 }