feat: Moves gumps out of the core (#1916)

> [!Important]
> **Developer Note**
> This code change will **completely move gumps out of the core**


### Summary

- Adds `GetGumps()` convenience which exposes methods to Find/Close/Send multiple gumps. This helper is a performance improvement by eliminating the Dictionary<Player, List> lookup for gumps.

Projects/UOContent/Gumps/ToTAdminGump.cs

@@ -31,6 +31,8 @@ namespace Server.Gumps
 
         private readonly int m_ToTEras;
 
+        public override bool Singleton => true;
+
         public ToTAdminGump() : base(30, 50)
         {
             Closable = true;
@@ -123,11 +125,7 @@ namespace Server.Gumps
         [Usage("ToTAdmin"), Description("Displays a menu to configure Treasures of Tokuno.")]
         public static void ToTAdmin_OnCommand(CommandEventArgs e)
         {
-            ToTAdminGump tg;
-
-            tg = new ToTAdminGump();
-            e.Mobile.CloseGump<ToTAdminGump>();
-            e.Mobile.SendGump(tg);
+            e.Mobile.SendGump(new ToTAdminGump());
         }
     }
 }