Remove usage of previously un-used ItemID values.

Early on in the lifetime of randomizer, we hijacked a few unused ItemID values to represent `ITEM_SINGLE_MAGIC`, `ITEM_DOUBLE_MAGIC` and `ITEM_DOUBLE_DEFENSE`.

We now have an official path for introducing items that don't exist into their own item table (for this case, the randomizer item table)

We should migrate these to using that official path