fix: Magic NPCs now use spell range (#1870)

### Summary
- Drastically streamlines the spell targeting by collapsing the target classes into a single `SpellTarget<T>` class.
- Moves TargetRange to the spell itself so it can be used by MageAI.
- Changes range check in MageAI to use TargetRange. This should fix target acquisition bugs

Projects/UOContent/Spells/Fifth/PoisonField.cs

@@ -7,7 +7,7 @@ using Server.Mobiles;
 
 namespace Server.Spells.Fifth;
 
-public class PoisonFieldSpell : MagerySpell, ISpellTargetingPoint3D
+public class PoisonFieldSpell : MagerySpell, ITargetingSpell<IPoint3D>
 {
     private static readonly SpellInfo _info = new(
         "Poison Field",
@@ -57,7 +57,7 @@ public class PoisonFieldSpell : MagerySpell, ISpellTargetingPoint3D
 
     public override void OnCast()
     {
-        Caster.Target = new SpellTargetPoint3D(this, range: Core.ML ? 10 : 12);
+        Caster.Target = new SpellTarget<IPoint3D>(this);
     }
 }