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/Server/Gumps/Legacy/GumpEntry.cs

@@ -1,27 +0,0 @@
-using System.Buffers;
-using Server.Collections;
-
-namespace Server.Gumps;
-
-public abstract class GumpEntry
-{
-    private Gump m_Parent;
-
-    public Gump Parent
-    {
-        get => m_Parent;
-        set
-        {
-            if (m_Parent != value)
-            {
-                m_Parent?.Remove(this);
-
-                m_Parent = value;
-
-                m_Parent?.Add(this);
-            }
-        }
-    }
-
-    public abstract void AppendTo(ref SpanWriter writer, OrderedSet<string> strings, ref int entries, ref int switches);
-}