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.Tests/Tests/Skills/Tracking/TrackingGumpTests.cs

@@ -1,5 +1,5 @@
+using Server.Gumps;
 using Server.Mobiles;
-using Server.Network;
 using Server.SkillHandlers;
 using Server.Tests;
 using Server.Tests.Network;
@@ -20,7 +20,7 @@ public class TrackingGumpTests : IClassFixture<ServerFixture>
         var ns = PacketTestUtilities.CreateTestNetState();
 
         var expected = g.Compile(ns).Compile();
-        ns.SendDisplayGump(g, out var switches, out var entries);
+        ns.SendGump(g);
 
         var result = ns.SendPipe.Reader.AvailableToRead();
         AssertThat.Equal(result, expected);