In `test._test_multiprocessing` file, `HAVE_GETVALUE` constant is always `False`

Bug report

Bug description:

In the test._test_multprocessing, the HAVE_GETVALUE constant is always False because the HAVE_BROKEN_SEM_GETVALUE value does not exist in _multiprocessingmodule.

https://github.com/python/cpython/blob/6f7fb6c95ba9e4d5c1b86d0d4ad83d0cd495976b/Lib/test/_test_multiprocessing.py#L141-L142

On macOS, this value exists only in the flagsdict of _multiprocessing.

>>> import _mulitpocessing
>>> vars(_multiprocessing)
{'__name__': '_multiprocessing', '__doc__': None, '__package__': '', 
'__loader__':  ............ ,
.......
'SemLock': <class '_multiprocessing.SemLock'>,
'flags': {'HAVE_SEM_OPEN': 1, 'HAVE_BROKEN_SEM_GETVALUE': 1}}

Fix is easy and will permit to reactivate the second part of test_bounded_semaphore test.
https://github.com/python/cpython/blob/6f7fb6c95ba9e4d5c1b86d0d4ad83d0cd495976b/Lib/test/_test_multiprocessing.py#L1755-L1757

A new PR will be submitted soon.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS, Linux

Linked PRs

• gh-155540

从 Lib/test/_test_multiprocessing.py 中 HAVE_GETVALUE 的定义和 test_bounded_semaphore 开始。检查 _multiprocessing 在 macOS 上如何公开其 flags，然后运行相关的 multiprocessing 测试。完成的标准是 HAVE_GETVALUE 反映平台值，并且 test_bounded_semaphore 的第二部分处于启用状态且通过测试。