`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 PEP 544 should only be suggested as a historical document.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.)

Comienza con la documentación de typing.Protocol enlazada en el issue y compara sus indicaciones con PEP 544. Revisa los ejemplos y las explicaciones de Protocol para comprobar la cobertura solicitada de ABCMeta, abstractmethod y las referencias. Se considera terminado cuando los detalles relevantes orientados al usuario estén documentados y la referencia a PEP se presente como contexto histórico.