Allow enabling sand duping (#10191)

Because this exploit has been widely known for years and has not been fixed by Mojang, we decided that it was worth allowing people to toggle it on/off due to how easy it is to make it configurable.

It should be noted that this decision does not promise all future exploits will be configurable.

patches/server/0678-Add-API-for-item-entity-health.patch

@@ -0,0 +1,34 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jake Potrebic <jake.m.potrebic@gmail.com>
+Date: Sat, 28 Aug 2021 09:00:45 -0700
+Subject: [PATCH] Add API for item entity health
+
+== AT ==
+public net.minecraft.world.entity.item.ItemEntity health
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftItem.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftItem.java
+index 4a15c3786edbfeae3367c0b20fb6aee11d62aea6..1a291dd8a287db30e71dcb315599fc4b038764c4 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftItem.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftItem.java
+@@ -98,6 +98,21 @@ public class CraftItem extends CraftEntity implements Item {
+      public void setWillAge(boolean willAge) {
+         this.getHandle().age = willAge ? 0 : NO_AGE_TIME;
+      }
++
++    @Override
++    public int getHealth() {
++        return this.getHandle().health;
++    }
++
++    @Override
++    public void setHealth(int health) {
++        if (health <= 0) {
++            this.getHandle().getItem().onDestroyed(this.getHandle());
++            this.getHandle().discard(org.bukkit.event.entity.EntityRemoveEvent.Cause.PLUGIN);
++        } else {
++            this.getHandle().health = health;
++        }
++    }
+     // Paper end
+ 
+     @Override