[WIP] gh-141510: PEP 814: Add built-in frozendict type

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• Basic tests
• Bare minimum documentation
• Support frozendict in marshal, pickle, json, copy
• Replace dict with frozendict in many stdlib modules

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📚 Documentation preview 📚: https://cpython-previews--141508.org.readthedocs.build/

• Issue: PEP 814: Add built-in frozendict type #141510

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This PR was created mainly to play with PEP 814 implementation, not to be merged.

If PEP 814 is accepted, this PR should be splitted into smaller parts, easier to review.

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mypy / Run mypy on Lib/_pyrepl (pull_request)
mypy / Run mypy on Lib/tomllib (pull_request)

mypy fails with Name "frozendict" is not defined.

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Tests / Android (x86_64) (pull_request) does crash, I'm not sure why.

  0:01:27 [ 39/497] test.test_concurrent_futures.test_interpreter_pool
  E/libsigchain: reverting to SIG_DFL handler for signal 11, ucontext 0x72d5b7547ac0

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Tests / Android (x86_64) (pull_request) does crash, I'm not sure why.

It should be fixed by Add PyFrozenDict_Type to static_types commit.

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TODO: Provide better error on hashing a mutable value:

>>> fd = frozendict(x=[1])
>>> hash(fd)
...
TypeError: cannot use 'tuple' as a set element (unhashable type: 'list')

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This PR is a draft combining all changes to adopt frozendict in the stdlib. It's too big to be merged. I started to split this PR into smaller PRs with #144757 as a starting point: most basic PR just to add the frozendict type.