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/0005-Paper-config-files.patch

@@ -482,10 +482,10 @@ index 0000000000000000000000000000000000000000..c01b4393439838976965823298f12e47
 +}
 diff --git a/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java b/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java
 new file mode 100644
-index 0000000000000000000000000000000000000000..57e6e857c84234bf0c137058ae35e6fb0e9b124f
+index 0000000000000000000000000000000000000000..7a53374319d5495253f277199114eaf43097456d
 --- /dev/null
 +++ b/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java
-@@ -0,0 +1,309 @@
+@@ -0,0 +1,311 @@
 +package io.papermc.paper.configuration;
 +
 +import co.aikar.timings.MinecraftTimings;
@@ -635,6 +635,8 @@ index 0000000000000000000000000000000000000000..57e6e857c84234bf0c137058ae35e6fb
 +    public UnsupportedSettings unsupportedSettings;
 +
 +    public class UnsupportedSettings extends ConfigurationPart {
++        @Comment("This setting allows for exploits related to end portals, for example sand duping")
++        public boolean allowUnsafeEndPortalTeleportation = false;
 +        @Comment("This setting controls if players should be able to break bedrock, end portals and other intended to be permanent blocks.")
 +        public boolean allowPermanentBlockBreakExploits = false;
 +        @Comment("This setting controls if player should be able to use TNT duplication, but this also allows duplicating carpet, rails and potentially other items")