Netherite Upgrade from Piglin bartering

Aquiring Netherite gear while playing on a server became harder after version 1.20, now needing Netherite Upgrade that other players will quickly loot from nearby bastions.

This datapack adds Netherite Upgrade to Piglin Bartering at ~0.65% chance, so progression is no longer hindered if you are not the first one to enter the Nether.

I know it's not ideal solution, because it can prevent going to bastions at all and make players farm Upgrades in easy way using piglin farms, but I think for server purposes it does the job just right.