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/0798-Add-entity-knockback-API.patch

@@ -0,0 +1,22 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: MelnCat <melncatuwu@gmail.com>
+Date: Sun, 16 Oct 2022 12:10:17 -0700
+Subject: [PATCH] Add entity knockback API
+
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
+index e559af05c58b7d9c940cea9f48c0f4bd0aad756c..cb585a82e52697d84f3da25a150b663c8c286f58 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
+@@ -1073,5 +1073,11 @@ public class CraftLivingEntity extends CraftEntity implements LivingEntity {
+         }
+         throw new IllegalArgumentException(entityCategory + " is an unrecognized entity category");
+     }
++
++    @Override
++    public void knockback(double strength, double directionX, double directionZ) {
++        Preconditions.checkArgument(strength > 0, "Knockback strength must be > 0");
++        getHandle().knockback(strength, directionX, directionZ);
++    };
+     // Paper end
+ }