gh-133423: Avoid ref cycle among MagicMock and its magic methods

[ppwwyyxx]

The following tests pass:

./python -m test -v test_unittest

• Issue: unittest.mock.patch.object holds references for too long #133423

[python-cla-bot]

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[cjw296]

Looking at your original issue, it appears that your problems there are better addressed without changes to the Python core codebase?

Apologies if I'm misreading that.

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[ppwwyyxx]

We deliberately want to run certain resource-heavy tests in some cases, so the suggestion to use less resource is not ideal. Regardless, I suppose avoiding ref cycle is a general improvement worth adding.