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/Spells/Necromancy/SummonFamiliar.cs

@@ -69,7 +69,6 @@ public class SummonFamiliarSpell : NecromancerSpell
     {
         if (CheckSequence())
         {
-            Caster.CloseGump<SummonFamiliarGump>();
             Caster.SendGump(new SummonFamiliarGump(Caster, Entries, this));
         }
 
@@ -109,6 +108,8 @@ public class SummonFamiliarGump : Gump
 
     private readonly SummonFamiliarSpell _spell;
 
+    public override bool Singleton => true;
+
     public SummonFamiliarGump(Mobile from, SummonFamiliarEntry[] entries, SummonFamiliarSpell spell) : base(200, 100)
     {
         _from = from;
@@ -187,14 +188,12 @@ public class SummonFamiliarGump : Gump
             // That familiar requires ~1_NECROMANCY~ Necromancy and ~2_SPIRIT~ Spirit Speak.
             _from.SendLocalizedMessage(1061606, $"{entry.ReqNecromancy:F1}\t{entry.ReqSpiritSpeak:F1}");
 
-            _from.CloseGump<SummonFamiliarGump>();
             _from.SendGump(new SummonFamiliarGump(_from, SummonFamiliarSpell.Entries, _spell));
         }
         else if (entry.Type == null)
         {
             _from.SendMessage("That familiar has not yet been defined.");
 
-            _from.CloseGump<SummonFamiliarGump>();
             _from.SendGump(new SummonFamiliarGump(_from, SummonFamiliarSpell.Entries, _spell));
         }
         else