Add config setting for grindstone overstacking (#8156)

patches/server/Paper-config-files.patch

@@ -578,6 +578,8 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +        public boolean performUsernameValidation = true;
 +        @Comment("This setting controls if players should be able to create headless pistons.")
 +        public boolean allowHeadlessPistons = false;
++        @Comment("This setting controls if grindstones should be able to output overstacked items (such as cursed books).")
++        public boolean allowGrindstoneOverstacking = false;
 +    }
 +
 +    public Commands commands;

patches/server/Prevent-grindstones-from-overstacking-items.patch

@@ -13,7 +13,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
                  itemstack2 = this.mergeEnchants(itemstack, itemstack1);
                  if (!itemstack2.isDamageableItem()) {
 -                    if (!ItemStack.matches(itemstack, itemstack1)) {
-+                    if (!ItemStack.matches(itemstack, itemstack1) || itemstack2.getMaxStackSize() == 1) { // Paper - add max stack size check
++                    if (!ItemStack.matches(itemstack, itemstack1) || (itemstack2.getMaxStackSize() == 1 && !io.papermc.paper.configuration.GlobalConfiguration.get().unsupportedSettings.allowGrindstoneOverstacking)) { // Paper - add max stack size check & config value
                          this.resultSlots.setItem(0, ItemStack.EMPTY);
                          this.broadcastChanges();
                          return;