`Protocol` should be documented as using `ABCMeta` as metaclass

Documentation

Came up in #127648.

Currently the documentation for typing.Protocol doesn't mention that Protocol has ABCMeta in its metaclasses (indirectly via _ProtocolMeta) and that its methods can (should?) be marked with @abstractmethod. In fact, neither the string "ABCMeta" nor "abstractmethod" appear in the documentation for the typing module.

I also suggest to add @abstractmethod to the examples using a Protocol as that is probably a best practice.

Finally, the documentation for Protocol suggests to see PEP 544 for more details. I don't think this is particularly helpful. All information relevant for users should be in the main documentation. PEP 544 should only be suggested as a historical document. (And I don't suggest to directly link to the typing spec, either, although a general link at the top of the page would be useful.)

Commencez par la documentation de typing.Protocol liée dans l’issue et comparez ses indications avec la PEP 544. Examinez les exemples et les explications de Protocol pour vérifier la couverture demandée de ABCMeta, abstractmethod et des références. Le travail est considéré comme terminé lorsque les détails pertinents destinés aux utilisateurs sont documentés et que la référence à la PEP est présentée comme un contexte historique.