This allows ClassDB to get the default values for inherited properties.
The `MissingNode` and `MissingResource` types are excluded from the create
dialog and the inspector's Resource selector.
Potentially resolves https://github.com/godotengine/godot/issues/101375
VisualShader now has a has_node_embeds function that runs through it's child nodes to find embedded resources via object properties. Conversion plugin uses this function to catch the error.
