Paint's Choosier Bartering

Changes since v1:

* Toggable feature (on by default): Show offers. If you hold a gold ingot, Piglins will stop and show you what they offer.
     * Toggable feature (on by default): Show known offers. Can make it so they only show what they've already bartered, unless you've bartered at least 4 times, in which case they'll show all they barter.
     * Doesn't occur if a piglin has items in their inventory, due to the Piglin's inventory being bugged and would cause item duplication.
     * Doesn't occur if the piglin has nothing to barter due to running out of items to barter.

* Toggable feature (on by default): Limited stock. Piglins can now run out of items to barter!
     * Barter limits:
         * Common items like Blackstone & Soul Sand: 14-18 barters.
         * Uncommon items like String & Quartz: 6-10 barters.
         * Rare items like Ender Pearl & Iron Nugget: 2-6 barters.
         * Very rare items like Potions & Iron Boots: 1-5 barters.
         * Enchanted Book: 1-4 barters.
     * Piglins who have nothing left to barter will give you your gold back (but will also try to pick it back up).
         * They will also show the barrier particle.
 
* Toggable feature (on by default): Self-Armor. Piglins who get bartered with a lot will equip themselves with gold armor, if they aren't already wearing it.
     * The number of gold it takes to get armor is the same amount as it takes a player to craft it. eg. 4 = boots.
     * Piglins will always go for boots, helmet, leggings and chestplate in that order. They will never save their gold for something more expensive because they are impatient.
     * They might run out of stock before getting all the armor pieces, but it's unlikely.

* How to toggle features: Use /function paint:pcb/gamerules/change
    * A chat prompt will let you toggle all the gamerules.

* pack_format is now 7.