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/0828-Add-Sneaking-API-for-Entities.patch

@@ -0,0 +1,29 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: dawon <dawon@dawon.eu>
+Date: Wed, 19 Oct 2022 23:31:53 +0200
+Subject: [PATCH] Add Sneaking API for Entities
+
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+index b7fceba1c7138a5c1d78bf058c9f2d32dbc1d292..69dc7d9cc9ebd681d842099e2de521fd11ff5242 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+@@ -872,6 +872,18 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
+         return Pose.values()[this.getHandle().getPose().ordinal()];
+     }
+ 
++    // Paper start
++    @Override
++    public void setSneaking(boolean sneak) {
++        this.getHandle().setShiftKeyDown(sneak);
++    }
++
++    @Override
++    public boolean isSneaking() {
++        return this.getHandle().isShiftKeyDown();
++    }
++    // Paper end
++
+     @Override
+     public SpawnCategory getSpawnCategory() {
+         return CraftSpawnCategory.toBukkit(this.getHandle().getType().getCategory());