Unify plain and type of for items

[sovdeeth]

Problem

type of has been misleading for users when used with items, as it only clears names and durability, rather than just returning a completely base item representative of the type. plain can return weird items when used with things that require ItemMeta to differentiate, like potions (returns uncraftable potion) and goat horns (always returns ponder).

Solution

Changes both expressions to use a new getBaseType method on ItemType that replaces aliasCopy. This copies over only the minimum necessary info (potion meta info and goat horn info) to differentiate items. This means plain strength potion now actually returns a strength potion, and type of diamond sword of mending returns a diamond sword without enchants.

I don't expect this to break anything for the user, but I'm not entirely sure it is 100% safe. Testers are welcome! I've done testing around potions and goat horns and enchantments, and it seems fine to me, but I'm not sure if there's some edge case I'm missing.

Testing Completed

regression test, manual testing

Supporting Information

There's a second option here, where type of always returns the item with no other identifying data. This may be more desirable for the type of could be interpreted as the material alone. However, this means type of strength potion is uncraftable potion, and type of strength potion is type of speed potion returns true. I don't think these changes are intuitive and could be breaking for users. I am open to counter-arguments, though.

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Completes: #8144
Related: none
AI assistance: none

[Efnilite]

looks good, could use a plain item test

[sovdeeth]

looks good, could use a plain item test

plain is already tested in quite a few places throughout the tests, but if you think a standalone is worthwhile i can do that too