Fix #544: Port to Python 3.14

[vstinner]

• _getattribute() API changed in Python 3.14.
• itertools.count() no longer supports pickle on Python 3.14: https://docs.python.org/dev/whatsnew/3.14.html#itertools
• Fix annotations test.

[vstinner]

_getattribute() API changed in Python 3.14: see python/cpython@1bb955a.

[vstinner]

I didn't add py314 to tox.ini since Python 3.14 is only at alpha1 stage, it might be early to add it to tox. Tell me if you want me to add it.

[serhiy-storchaka]

Why simply not add the own implementation of _getatribute()?

[vstinner]

Why simply not add the own implementation of _getatribute()?

Python 3.13:

def _getattribute(obj, name):
    top = obj    
    for subpath in name.split('.'):
        if subpath == '<locals>':
            raise AttributeError("Can't get local attribute {!r} on {!r}"
                                 .format(name, top))
        try:
            parent = obj
            obj = getattr(obj, subpath)
        except AttributeError:
            raise AttributeError("Can't get attribute {!r} on {!r}"
                                 .format(name, top)) from None
    return obj, parent

Python 3.14:

def _getattribute(obj, dotted_path):
    for subpath in dotted_path:
        obj = getattr(obj, subpath)
    return obj

I don't know which implementation is the best, I don't know the cloudpickle project, so I prefer to continue calling what's available in pickle.

At least, I can say that Python 3.14 implementation is the simplest :-)