`atexit` module breaks refleak check

Bug report

Bug description:

If the test registers a callback with atexit module, refleak test will consider it a leak.

    def test_refleak(self):
        atexit.register(lambda: None)

This is the root cause of the buildbot failure of https://github.com/python/cpython/pull/139185. It's a couple of coincidences that caused the seemingly unrelated issue. Basically, clearing the module cache in test_zipimport made the module-level code in rlcompleter, which includes a register to atexit, run more than once.

There are a few possible approaches to fix this, but I did not find the solution that I'm immediately happy with.

I consider this a test framework bug as this should be a valid behavior. The ideal solution is to keep the atexit callbacks before running test in a loop and restore it after. However, atexit does not provide such an interface, public or private. You can either clear it or run it. The callbacks are stored in a state of the interpreter and we don't have any access to it.

Without that, we either need to somehow calculate the allocated memory by atexit, or hope that no one writes a test that writes to atexit. Of course there might be other ways that I did not think of.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-139305
• gh-139357

• [3.14] gh-139305 was backported as part of gh-139280

从 refleak 测试框架以及注册 atexit 回调的 test_refleak 示例开始。检查 test_zipimport 清除模块缓存如何导致 rlcompleter 的模块级注册被重复执行，并查看关联的 PR gh-139305 和 gh-139357，了解已有的工作。完成的标准是，有效的 atexit 注册不再显示为 refleaks。