Refactor Alchemist Stones

[Twintop]

Alchemist Stone data exists in each module, including a list of valid itemIds. Refactor this to be a spell that is stored in some shared place, and, move logic for checking if we have an alchemist stone equipped to there, too.

Other considerations:

• Add support for all Alchemist Stones, not just ones from Shadowlands and The War Within. See: https://www.wowhead.com/beta/spell=17619/alchemist-stone#used-by-item
• Check if the character has Alchemy as a profession before doing a check for the stone being equipped.

[Twintop]

Done in Beta, minus checking for Alchemy as a profession.