Show data attributes not in the aron type in MemoryViewer

Data attributes that aren't in the aron type definition for the object are currently hidden when "Use Type Information" is selected in the MemoryViewer. This MR fixes this by making the TypedDataTreeBuilder show an item with no type information instead and delegating any untyped dicts or lists to an untyped DataTreeBuilder.

Note that this functionality isn't tested yet because I haven't found any untyped members in the examples (and don't really want to hack them into the official ExampleMemoryClient). @fratty do you know where I could find some, since you requested this feature?