Remove index from BaseType, DeclaringType

All types will need to eventually be fully generic. Therefore, we need
to eliminate indices when referring to types, and also be very lazy when
accessing TypeInfo properties so that we don't access uninitialized
types during model creation.

Il2CppInspector.Common/Reflection/MemberInfo.cs

@@ -20,8 +20,7 @@ namespace Il2CppInspector.Reflection {
         public CustomAttributeData[] GetCustomAttributes(string fullTypeName) => CustomAttributes.Where(a => a.AttributeType.FullName == fullTypeName).ToArray();
 
         // Type that this type is declared in for nested types
-        protected int declaringTypeDefinitionIndex { private get; set; } = -1;
-        public TypeInfo DeclaringType => declaringTypeDefinitionIndex != -1? Assembly.Model.TypesByDefinitionIndex[declaringTypeDefinitionIndex] : null;
+        public virtual TypeInfo DeclaringType { get; private set; }
 
         // What sort of member this is, eg. method, field etc.
         public abstract MemberTypes MemberType { get; }
@@ -36,11 +35,9 @@ namespace Il2CppInspector.Reflection {
         protected MemberInfo(Assembly asm) => Assembly = asm;
 
         // For lower level members, eg. fields, properties etc. and nested types
-        protected MemberInfo(TypeInfo declaringType = null) {
-            if (declaringType != null) {
-                Assembly = declaringType.Assembly;
-                declaringTypeDefinitionIndex = declaringType.Index;
-            }
+        protected MemberInfo(TypeInfo declaringType) {
+            Assembly = declaringType.Assembly;
+            DeclaringType = declaringType;
         }
 
         public override string ToString() => Name;