functools.partial should use PEP612 ParamSpec (depends on #8708)

Currently, functools.partial's __call__ method takes *args: Any, **kwargs: Any and returns _T (a TypeVar for the return type of the callable the partial is wrapping). This is decent, but matching the parameter typing would make this more useful in more situations.

I can sort of see how to deal with this, although I'll admit I'm unsure how to make this generically work. I imagine you could probably deal with some number of Concatenates (maybe up to 5 or 10) to deal with most cases. It's possible fixing this requires another PEP to allow an arbitrary-length Concatenate-type pattern.

Related to https://github.com/python/mypy/issues/1484

Inizia da stdlib/functools.pyi intorno alla riga 75 e rivedi i concetti ParamSpec e Concatenate della PEP 612. Verifica la dipendenza dall'issue #8708 e dalla relativa issue di mypy prima di decidere se la tipizzazione richiesta sia esprimibile. Il lavoro è completato quando call di functools.partial conserva la tipizzazione dei parametri del callable sottostante invece di usare Any.