moving apidiff out of preview (#3595)

release-notes/3.0/api-diff/.Net/3.0.0_System.Reflection.md

@@ -0,0 +1,37 @@
+# System.Reflection
+
+``` diff
+ namespace System.Reflection {
+     public abstract class Assembly : ICustomAttributeProvider, ISerializable {
++        public virtual bool IsCollectible { get; }
+     }
+     public class CustomAttributeData {
+-        public Type AttributeType { get; }
++        public virtual Type AttributeType { get; }
+     }
+-    public struct CustomAttributeNamedArgument
++    public readonly struct CustomAttributeNamedArgument
+-    public struct CustomAttributeTypedArgument
++    public readonly struct CustomAttributeTypedArgument
++    public interface ICustomTypeProvider {
++        Type GetCustomType();
++    }
+     public abstract class MemberInfo : ICustomAttributeProvider {
++        public virtual bool IsCollectible { get; }
+     }
+     public enum MethodImplAttributes {
++        AggressiveOptimization = 512,
+     }
+     public sealed class ReflectionTypeLoadException : SystemException, ISerializable {
++        public override string Message { get; }
++        public override string ToString();
+     }
+     public class TypeDelegator : TypeInfo {
++        public override bool IsCollectible { get; }
+     }
+     public abstract class TypeInfo : Type, IReflectableType {
++        protected TypeInfo();
+     }
+ }
+```
+