Remove Anvil Prior Work Penalty

Removes the 'prior work' penalty applied to items when repairing or enchanting them in the anvil.
No longer will you be penalized for using the anvil for its intended purpose! No longer will you be forced to trade for Mending to use your tools for any reasonable period of time!

Simple, highly optimized, and multiplayer friendly. The datapack only runs commands while the Anvil UI is open to prevent unnecessary lag. Additionally, no extra components are added to your items (preventing weird issues where items don't stack).