Remove current throwback implementation

[albertopoljak]

It is dropped, too much work and it tends to be very buggy.
Current implementation is also buggy, since there is no collision for enemies it can push enemies off screen and trough walls.

If it's not gonna be implemented then a simple collision check for wall hit needs to be performed after pushback that will just reset enemy change_x, change_y to 0 AND move them to nearest passable tile (if we don't move them we can spam them into wall.)