stubgen (stubgenc): Support for tp_getset style C properties

Feature

Currently for C extensions, attributes of a C type originating from tp_getset are not recognized as a class property.
It would be nice to still parse the docstring in such cases, to infer types.

Pitch

As far as I understand, this is due to mypy.stubgenc.is_c_property looking for the fget attribute (the tp_getset style attributes dont have such an attribute - at least in my case, python 3.8).

I am not sure how to properly add checks for such a case (is just removing the check hasattr(obj, 'fget') enough?)

Would be glad for any input here (Am I missing something? Is there a good strategy to add support for tp_getset style attributes?). I would offer to implement the feature, if you think this would make sense.

Inizia da mypy.stubgenc.is_c_property e analizza come stubgen riconosce le proprietà e legge i relativi docstrings. Determina in che modo gli attributi C nello stile di tp_getset differiscono dal caso esistente, quindi verifica che i relativi docstrings possano essere utilizzati per inferire i tipi delle proprietà senza influire sugli altri attributi delle estensioni C.