gh-82062: correctly set module for built-in instance methods in inspect.signature()

[skirpichev]

The __module__ attribute is missing for instance methods in extension modules, so instead we use in this case __objclass__.__module__.

• Issue: __text_signature__ parser doesn't handle globals in extension module #82062

[skirpichev]

Alternatively, we could set the __module__ attribute for instance methods, see #115232. Right now for built-in instance methods its missing (c.f. pure-python classes):

>>> int.to_bytes.__module__
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'method_descriptor' object has no attribute '__module__'. Did you mean: '__reduce__'?

[skirpichev]

@serhiy-storchaka, I hope I did requested changes.

[serhiy-storchaka]

LGTM.