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/Items/Skill Items/Magical/Misc/Moongate.cs

@@ -157,7 +157,6 @@ public partial class Moongate : Item
                 from.SendSound(0x20E, from);
             }
 
-            from.CloseGump<MoongateConfirmGump>();
             from.SendGump(new MoongateConfirmGump(from, this));
         }
         else
@@ -265,7 +264,6 @@ public partial class ConfirmationMoongate : Moongate
     {
         if (GumpWidth > 0 && GumpHeight > 0 && TitleNumber > 0 && Message?.IsEmpty == false)
         {
-            from.CloseGump<WarningGump>();
             from.SendGump(
                 new WarningGump(
                     TitleNumber,
@@ -275,7 +273,8 @@ public partial class ConfirmationMoongate : Moongate
                     GumpWidth,
                     GumpHeight,
                     okay => Warning_Callback(from, okay)
-                )
+                ),
+                true
             );
         }
         else
@@ -307,6 +306,8 @@ public class MoongateConfirmGump : Gump
     private Mobile _from;
     private Moongate _gate;
 
+    public override bool Singleton => true;
+
     public MoongateConfirmGump(Mobile from, Moongate gate) : base(Core.AOS ? 110 : 20, Core.AOS ? 100 : 30)
     {
         _from = from;