frozendict cannot be pickled with protocols 0 and 1

Bug report

frozendict cannot be pickled with protocols 0 and 1, while frozenset can:

>>> import pickle
>>> pickle.dumps(frozendict(a=1), 0)
Traceback (most recent call last):
  ...
TypeError: cannot pickle 'frozendict' object
>>> pickle.dumps(frozenset({1}), 0)  # works

Protocols 2 through 5 already work. frozendict only defines __getnewargs__,
a protocol-2-and-later mechanism, while frozenset defines __reduce__, which
works at every protocol.

CPython versions tested on:

3.16 (main)

Operating systems tested on:

Linux, macOS

Linked PRs

• gh-155325

Comece comparando o comportamento de getnewargs de frozendict com o de reduce de frozenset e o ponto de entrada pickle.dumps para os protocolos 0 e 1. Adicione cobertura de regressão para ambos os protocolos e confirme que frozendict pode ser serializado e restaurado, verificando também o PR vinculado existente gh-155325 quanto ao trabalho já em andamento.