Add another obstacle for Warehouse Entrance super blocks

[blkerby]

Various strats in this room require either 1, 2, or 3 of the Super blocks to be broken. Currently it isn't modeled very precisely because there's only one obstacle ("A") and it represents clearing all 3 Super blocks. I think it would probably be sufficient to have two obstacles, one for the bottom Super block, and one for the top two. Then the strats could be written in a way that would logically require fewer Supers in some situations (e.g. crossing the room, unlocking a door, and returning).