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/0840-Win-Screen-API.patch

@@ -0,0 +1,38 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Lama06 <andreasprues36@gmail.com>
+Date: Sat, 21 Jan 2023 13:53:23 +0100
+Subject: [PATCH] Win Screen API
+
+== AT ==
+public net.minecraft.server.level.ServerPlayer seenCredits
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+index 69917a56fc05f8c16a1302fe331993e8d49889b9..4996776287c58039507ad2eda9d59e3fd13c08a8 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+@@ -1214,6 +1214,25 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
+         this.getHandle().connection.send(packet);
+     }
+ 
++    // Paper start
++    @Override
++    public void showWinScreen() {
++        if (getHandle().connection == null) return;
++        var packet = new ClientboundGameEventPacket(ClientboundGameEventPacket.WIN_GAME, 1);
++        getHandle().connection.send(packet);
++    }
++
++    @Override
++    public boolean hasSeenWinScreen() {
++        return getHandle().seenCredits;
++    }
++
++    @Override
++    public void setHasSeenWinScreen(boolean hasSeenWinScreen) {
++        getHandle().seenCredits = hasSeenWinScreen;
++    }
++    // Paper end
++
+     @Override
+     public void setRotation(float yaw, float pitch) {
+         // Paper start - Teleport API