Add enchanted name tags in loot tables

Enchanted name tags would be obtainable only as loot and would not be craftable.

An enchanted name tag would generate with one enchantment, but this could be changed in an anvil if you don't like the original enchantment that it comes with.

You would also be able to transform an enchanted name tag back into a normal one (permanently) using a grindstone.

If an enchanted name tag were put on a mob, then that enchantment would be "always on". For example, with Efficiency name tag on a Villager, that Villager would always have Efficiency operating even if it doesn't use any tools. Or an Iron Golem given Smite would always be able to Smite undead even though it does not wield a sword or axe.