Allow adding attributes to any members in partial types

[alrz]

Assuming that this is autogenerated:

partial class X {
    public string Property { get; }
    public void Method() { }
}

It is helpful that we can add attributes to the type,

[Attribute] // works
partial class X {
   [Attribute] // safe to allow?
   public partial string Property { get; } // signature must exactly match
   [Attribute]
   public partial void Method();
}

But this is not possible for members. I think since partial is explicitly specified on both types, this doesn't lead to unexpected behavior.