Pathlib.iterdir semantics change dramatically under Python 3.13

Bug report

Bug description:

This code behaves very differently on Python 3.13 than 3.12:

(p for p in pathlib.Path('does-not-exist').iterdir())

 🐚 py -3.12 -c "import pathlib; (p for p in pathlib.Path('does-not-exist').iterdir())"
 🐚 py -3.13 -c "import pathlib; (p for p in pathlib.Path('does-not-exist').iterdir())"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import pathlib; (p for p in pathlib.Path('does-not-exist').iterdir())
                                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/homebrew/Cellar/python@3.13/3.13.1/Frameworks/Python.framework/Versions/3.13/lib/python3.13/pathlib/_local.py", line 575, in iterdir
    with os.scandir(root_dir) as scandir_it:
         ~~~~~~~~~~^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: 'does-not-exist'

In Python 3.12, the generator expression was evaluated lazily, not invoking path.iterdir() until the generator was consumed. On 3.13, at least a portion of the generator is evaluated, triggering the exception when the dir does not exist.

I discovered this issue in https://github.com/jaraco/jaraco.develop/issues/26.

I looked at What's New for Python 3.13, and there's only one mention of generator expressions regarding mutation of locals in generator expressions, which doesn't seem to be relevant here.

That change mentions https://github.com/python/cpython/issues/74929, so maybe that change is also implicated in the change in execution order.

CPython versions tested on:

3.13

Operating systems tested on:

macOS

Reproduzieren Sie das Verhalten von Generatorausdrücken unter Python 3.12 und 3.13 und untersuchen Sie anschließend pathlib/_local.py um Zeile 575 sowie die in issue 74929 diskutierte Semantik von Generatorausdrücken. Bestimmen Sie, ob die geänderte Auswertungsreihenfolge beabsichtigt ist oder eine Regression darstellt, und fügen Sie einen fokussierten Regressionstest hinzu, der den erwarteten Zeitpunkt des FileNotFoundError zeigt.