chore(content): Cleans up abilities and some spell timers (#427)

- [X] Exposes Index/Count on the timer.
- [X] Cleans up abilities
- [X] Combines some spell context/info objects with their timers to reduce allocations
- [X] Fixes a bug where immolating weapon both finishes effect or stops in the wrong order due to a race condition.

Projects/UOContent/Spells/Sixth/Invisibility.cs

@@ -62,19 +62,21 @@ namespace Server.Spells.Sixth
 
                 var duration = TimeSpan.FromSeconds(1.2 * Caster.Skills.Magery.Fixed / 10);
 
-                Timer t = new InternalTimer(m, duration);
-
                 BuffInfo.RemoveBuff(m, BuffIcon.HidingAndOrStealth);
                 BuffInfo.AddBuff(m, new BuffInfo(BuffIcon.Invisibility, 1075825, duration, m)); // Invisibility/Invisible
 
-                m_Table[m] = t;
-
-                t.Start();
+                m_Table[m] = Timer.DelayCall(duration, EndInvisiblity, m);
             }
 
             FinishSequence();
         }
 
+        private static void EndInvisiblity(Mobile m)
+        {
+            m.RevealingAction();
+            RemoveTimer(m);
+        }
+
         public override bool CheckCast()
         {
             if (DuelContext.CheckSuddenDeath(Caster))
@@ -100,22 +102,5 @@ namespace Server.Spells.Sixth
                 t.Stop();
             }
         }
-
-        private class InternalTimer : Timer
-        {
-            private readonly Mobile m_Mobile;
-
-            public InternalTimer(Mobile m, TimeSpan duration) : base(duration)
-            {
-                Priority = TimerPriority.OneSecond;
-                m_Mobile = m;
-            }
-
-            protected override void OnTick()
-            {
-                m_Mobile.RevealingAction();
-                RemoveTimer(m_Mobile);
-            }
-        }
     }
 }