Add reproducibility test for `gzip.compress()`

The issue https://github.com/python/cpython/issues/112346 was reported, which was a failure to keep reproducibility in gzip module output from Python 3.10 to 3.11.

There was a fix discussed and rejected in https://github.com/python/cpython/issues/112346

I think it makes sense not to actually change things back, but failing to merge the PR means we also failed to add unit tests.

Can we please add a general-purpose, fragile reproducibility test for the gzip module, so that this problem does not recur?

Ex. test that the output of gzip.compress("Hello world") remains stable

def test_gzip_reproducibility():
    """If this test fails, gzip.compress does not give reproducible output. Either fix that, or document the change in What's New and change the constant 'expected' below."""
    expected = b'\x1f\x8b\x08\x00\xa2\xd2\xe1g\x02\xff\xf3H\xcd\xc9\xc9W(\xcf/\xcaI\x01\x00R\x9e\xd6\x8b\x0b\x00\x00\x00'
    assert gzip.compress(b"Hello world") == expected

    expected = 
b'\x1f\x8b\x08\x00\x00\x00\x00\x00\x02\xff\xf3H\xcd\xc9\xc9W(\xcf/\xcaI\x01\x00R\x9e\xd6\x8b\x0b\x00\x00\x00'
    assert gzip.compress(b"Hello world", mtime=0) == expected    

Linked PRs

• gh-151214

Xem lại PR được liên kết gh-151214 và tìm các bài kiểm thử hiện có của mô-đun gzip trước khi bắt đầu. Thêm các kiểm tra tính tái lập cho gzip.compress() được nêu trong issue, sau đó xác nhận rằng các đầu ra dự kiến vẫn ổn định và ghi nhận mọi thay đổi có chủ đích trong What's New.