stubtest and @deprecated

Bug Report

The @warnings.deprecated decorator adds a few dunders to classes it decorates. This causes stubtest to complain about differences between stub and implementation, unless these changes are added manually to the stubs. I think we should special case @deprecated to ignore these differences.

To Reproduce

For example, adding the following test to StubtestUnit:

    @collect_cases
    def test_deprecated(self) -> Iterator[Case]:
        yield Case(
            stub="""
            from warnings import deprecated

            @deprecated("")
            class Foo: ...
            """,
            runtime="""
            from warnings import deprecated

            @deprecated("")
            class Foo:
                pass
            """,
            error=None,
        )

causes the following error when running the tests with Python 3.13:

E           AssertionError: error: test_module.Foo.__deprecated__ is not present in stub
E             Stub: in file test_module.pyi
E             MISSING
E             Runtime:
E             ''
E             
E             error: test_module.Foo.__init_subclass__ is not present in stub
E             Stub: in file test_module.pyi
E             MISSING
E             Runtime: in file /opt/pyenv/versions/3.13.8/lib/python3.13/warnings.py:621
E             def (*args, **kwargs)
E             
E             error: test_module.Foo.__new__ is not present in stub
E             Stub: in file test_module.pyi
E             MISSING
E             Runtime: in file /opt/pyenv/versions/3.13.8/lib/python3.13/warnings.py
E             def (*args, **kwargs)
E             
E             Found 3 errors (checked 1 module)
E             
E           assert {'test_module....Foo.__new__'} == set()
E             
E             Extra items in the left set:
E             'test_module.Foo.__deprecated__'
E             'test_module.Foo.__new__'
E             'test_module.Foo.__init_subclass__'
E             Use -v to get more diff

Interestingly, this is different from what we see in typeshed (python/typeshed#14893):

error: jwcrypto.jwt.JWTMissingKeyID.__init_subclass__ is inconsistent, stub does not have *args parameter "args"
Stub: in file /home/runner/work/typeshed/typeshed/stubs/jwcrypto/jwcrypto/jwt.pyi:139
def (cls: type[builtins.object])
Runtime: in file /opt/hostedtoolcache/Python/3.13.8/x64/lib/python3.13/warnings.py:621
def (*args, **kwargs)

Your Environment

• Mypy version used: master for the test above, 1.18.2 in typeshed CI
• Mypy command-line flags:
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.13

Inizia con il test proposto in StubtestUnit e riproducilo su Python 3.13. Traccia il confronto di stubtest tra le classi decorate con warnings.deprecated, quindi fai passare il test ignorando solo le differenze aggiunte dal decoratore.