Keep Head Names

Datapack continuation of Keep Head Names for Minecraft 1.21+

While MC-174496 has been fixed in 1.21, lore, item_name* and custom_data components are not kept when placing and mining player heads.

This datapack fixes just that.
It is unlikely for this datapack to break any time soon, so don't expect regular updates.

* Not to be confused with custom_name.
custom_name is the name given by an anvil, which is italics by default and can also be removed by an anvil.
item_name essentially replaces the item's original name (no italics, no way to change it in survival).