fix: Fixes various memory leaks and spells (#1786)

### Summary
- Fixes various memory leaks related to spells
- Fixes Spell Plague
- Added ability to determine if `sdi` should take effect for Spell Damage.
- Fixes animal form timer ticking non-stop while logged out.

Projects/UOContent/Mobiles/BaseCreature.cs

@@ -2395,13 +2395,17 @@ namespace Server.Mobiles
                 AnimateDeadSpell.Unregister(m_SummonMaster, this);
             }
 
+            if (Summoned && SummonMaster != null)
+            {
+                SummonFamiliarSpell.Unregister(SummonMaster, this);
+            }
+
             if (MLQuestSystem.Enabled)
             {
                 MLQuestSystem.HandleDeletion(this);
             }
 
             UnsummonTimer.StopTimer(this);
-
             StaminaSystem.RemoveEntry(this as IHasSteps);
 
             base.OnAfterDelete();