Remove unnecessary durability check in ItemStack#isSimilar

[MrPowerGamerBR]

I know that this looks like a stupid optimization that doesn't do anything, but hear me out: getDurability() ain't free, when you call getDurability(), it calls getItemMeta(), which then allocates a new ItemMeta or clones the current item's item meta.

However, this means that we are unnecessarily allocating useless ItemMeta objects if we are comparing one or more items that don't have any durability (if they had durability, they would have a non-null meta), and this impact can be noticed if one of your plugins has a canHoldItem function that checks if a inventory can hold an item by looping thru the player's inventory, especially if the plugin is checking this multiple times in a tick.

To avoid this, we can just... not check for the item's durability! Don't worry, the durability of the item is checked when it checks if both item metas are equal.

This is a leftover from when checking for the item's durability was "free" because the durability was stored in the ItemStack itself, this was changed in Minecraft 1.13, however the isSimilar(...) method hasn't been changed since it was added in 2012.

Of course, maybe this patch is a bit useless? There is a performance benefit if you remove that call since you avoid initializing/cloning a ItemMeta if one or both of the items have a null ItemMeta + removes a deprecated call + improves the code to match how items work in a post-1.13 world, but the benefit is so so so smol (really only helps plugins that are constantly checking if an item is similar to another, which is my case, where one of my plugins allows players to "quick harvest" their farms, and for each crop it needs to check if the drops fits on their inventory) that maybe it could just be ignored, after all, there's also the work of maintaining this diff to fix something that just boils down to "well now its correct and there is a super tiny perf improvement". (Maybe this should be upstreamed to Spigot since they are the ones who are maintaining Bukkit? but paper my beloved tho...)

(The reason I found out that this had a performance impact was because the getDurability() was using 0.08ms each tick in one of my plugins according to spark... yeah, sadly it ain't a super big crazy optimization, the performance impact would be bigger if you have more plugins using isSimilar(...) tho, something something pick a function and make it fast or something like that)

Keep in mind that CraftItemStack does override isSimilar(), and the overriden method also checks getDurability(). However, CraftItemStack getDurability() actually gets the damage directly from the NBT tags. Maybe both checks should be removed? "oh but if CraftItemStack overrides this method then your patch is USELESS!!!" actually not because you initialize the ItemStack class directly, and CraftItemStack delegates to ItemStack's isSimilar() if the stack being compared is not a CraftItemStack, see this debug log: [org.bukkit.craftbukkit.v1_20_R2.inventory.CraftItemStack] CraftItemStack isSimilar comparing ItemStack{CRAFTING_TABLE x 1} (class org.bukkit.craftbukkit.v1_20_R2.inventory.CraftItemStack) to ItemStack{BEETROOT x 1} (class org.bukkit.inventory.ItemStack)

Example of a plugin code that uses isSimilar(...):

fun Inventory.canHoldItem(stack: ItemStack?): Boolean {
	if (stack == null) { return true }
	if (stack.type == Material.AIR) { return true }
	val storageContents = this.storageContents
	if (storageContents != null) {
		for (invItem in storageContents) {
			if (invItem == null) return true // Empty slot!
			if (invItem.isSimilar(stack)) { // 
				if (invItem.maxStackSize >= invItem.amount + stack.amount) {
					// Yes, we can add the items to this stack!
					return true
				}
			}
		}
	}
	return false
}

[Machine-Maker]

This looks good to me. Confirmed that isSimilar still functions correctly when comparing damaged items.

It did make me go looking for other places ItemStack#getDurability is still used, and there are several which probably should also be reworked at some point, but that doesn't have to be here.