Scripts/Player: Add OnMapChanged to PlayerScripts (after map changed)

Core/Dungeon Finder: Use OnMapChanged script to cast/remove Luck of the draw
- Also move code to force party update to LfgPlayerScript
- Remove some obsolete Lfg code after recent commits

src/server/game/Scripting/ScriptMgr.h

@@ -754,6 +754,9 @@ class PlayerScript : public UnitScript
 
         // Called when a player switches to a new zone
         virtual void OnUpdateZone(Player* /*player*/, uint32 /*newZone*/, uint32 /*newArea*/) { }
+
+        // Called when a player changes to a new map (after moving to new map)
+        virtual void OnMapChanged(Player* /*player*/) { }
 };
 
 class GuildScript : public ScriptObject