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/Engines/Spawners/BaseSpawner.cs

@@ -4,6 +4,7 @@ using System.Reflection;
 using System.Text.Json;
 using ModernUO.Serialization;
 using Server.Commands;
+using Server.Gumps;
 using Server.Items;
 using Server.Json;
 using Server.Mobiles;