Implements basic method introspection

[Tpt]

Implementation notes:

• I am not sure about the decorators for class attributes. I am using the @classmethod\n@property combination that got removed in Python 3.11. I don't see a clean way to do it in the next Python versions. It's possible that type checkers work properly with it, we will need to check but I would prefer to focus on other things for now.
• When we introspect the class definition (#[pyclass] macro) we don't know the list of method so each method is generating its own introspection fragment with a "parent" attribute that connects a method to its class. We will likely reuse it again for nested classes used in complex enums.
• We are generating a / after the self or cls argument even (if they are not other positional-only arguments). It's not nice but syntactically correct.
• I have not tested all magic methods

[bschoenmaeckers]

I am not sure about the decorators for class attributes. I am using the @classmethod\n@property combination that got removed in Python 3.11. I don't see a clean way to do it in the next Python versions. It's possible that type checkers work properly with it, we will need to check but I would prefer to focus on other things for now.

Should we run a type-checker in the CI to verify the generated types?

[Tpt]

Should we run a type-checker in the CI to verify the generated types?

Yes, I am planning to do it when the implementation will be a bit more feature complete. At this stage it will complain a lot about missing elements in the stubs.