Implement difficulty balancing for enemy randomizer

[LagoLunatic]

Once enemy randomizer is always beatable, it should also have some system to balance enemy difficulty across rooms, not just whether they're beatable.

For example, each enemy type could be assigned a rating of 1-10 for how hard it is to fight. Then every vanilla room's difficulty could be automatically calculated by summing up the rating of each enemy in the room. Enemy rando should then try to limit how much the room's difficulty changes compared to vanilla within a multiplier range. e.g. 0.5x-1.0x for easy mode, 0.5x-2.0x for normal mode, 1.0x-3.0x for hard mode.