pkgutil direct use of zipimport._zip_directory_cache is no longer safe

Bug report

Bug description:

pkgutil directly uses zipimport._zip_directory_cache, in this block:

       def iter_zipimport_modules(importer, prefix=''):
           dirlist = sorted(zipimport._zip_directory_cache[importer.archive])

since https://github.com/python/cpython/pull/103208 , this is no longer safe, because that made zipimport no longer always refresh the cache on invalidation. I think that if the cache has been invalidated but not accessed 'normally' since then, this direct access attempt can cause a crash as it doesn't trigger a refresh:

E           KeyError: '/tmp/dask-scratch-space/scheduler-belyj1dp/myfile.zip'

I observed this in the test suite for dask-distributed - see https://github.com/dask/distributed/issues/8708 - but it seems like a general issue, and @desmondcheongzx asked me to file an issue, so here it is. That test suite hits it in a test that runs async and creates archives under the same name repeatedly, but there are probably other ways to hit this, I guess.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-121705

從 pkgutil.iter_zipimport_modules 和 issue 中描述的對 zipimport._zip_directory_cache 的直接存取開始；將其與 CPython PR 103208 引入的快取失效行為進行比較。重現 dask-distributed issue 8708 中的重複封存檔情境，並驗證由此產生的 KeyError 不再發生。