(BREAKING) Replace structs with classes

Framework/Editor/V1/AacAnimatorNode.cs

@@ -1,5 +1,3 @@
-using System;
-using System.Collections.Generic;
 using UnityEngine;
 
 // ReSharper disable once CheckNamespace
@@ -16,9 +14,6 @@ namespace AnimatorAsCode.V1
         protected readonly AacFlStateMachine ParentMachine;
         protected readonly IAacDefaultsProvider DefaultsProvider;
 
-        // TODO: What is this for???
-        protected Dictionary<Type, object> behaviorCache = new Dictionary<Type, object>();
-
         protected AacAnimatorNode(AacFlStateMachine parentMachine, IAacDefaultsProvider defaultsProvider)
         {
             ParentMachine = parentMachine;