Add /paper dumplisteners command (#8507)

Co-authored-by: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
Co-authored-by: TwoLeggedCat <80929284+TwoLeggedCat@users.noreply.github.com>

patches/api/0409-Add-paper-dumplisteners-command.patch

@@ -0,0 +1,37 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Warrior <50800980+Warriorrrr@users.noreply.github.com>
+Date: Sat, 19 Nov 2022 19:46:44 +0100
+Subject: [PATCH] Add /paper dumplisteners command
+
+
+diff --git a/src/main/java/org/bukkit/event/HandlerList.java b/src/main/java/org/bukkit/event/HandlerList.java
+index ed78cca71f83b296d082d0af147ca8d622c7606a..2292bd460ce2be113beb4ba6b4eb19350060f01c 100644
+--- a/src/main/java/org/bukkit/event/HandlerList.java
++++ b/src/main/java/org/bukkit/event/HandlerList.java
+@@ -33,6 +33,13 @@ public class HandlerList {
+      */
+     private static ArrayList<HandlerList> allLists = new ArrayList<HandlerList>();
+ 
++    // Paper start
++    /**
++     * Event types which have instantiated a {@link HandlerList}.
++     */
++    private static final java.util.Set<String> EVENT_TYPES = java.util.concurrent.ConcurrentHashMap.newKeySet();
++    // Paper end
++
+     /**
+      * Bake all handler lists. Best used just after all normal event
+      * registration is complete, ie just after all plugins are loaded if
+@@ -94,6 +101,12 @@ public class HandlerList {
+      * The HandlerList is then added to meta-list for use in bakeAll()
+      */
+     public HandlerList() {
++        // Paper start
++        java.lang.StackWalker.getInstance(java.util.EnumSet.of(java.lang.StackWalker.Option.RETAIN_CLASS_REFERENCE), 4)
++            .walk(s -> s.filter(f -> Event.class.isAssignableFrom(f.getDeclaringClass())).findFirst())
++            .map(f -> f.getDeclaringClass().getName())
++            .ifPresent(EVENT_TYPES::add);
++        // Paper end
+         handlerslots = new EnumMap<EventPriority, ArrayList<RegisteredListener>>(EventPriority.class);
+         for (EventPriority o : EventPriority.values()) {
+             handlerslots.put(o, new ArrayList<RegisteredListener>());