GH-94851: check refcnt of immortal objects after finalization

[kumaraditya303]

• Issue: Check for ref counting bugs in debug mode caused by immortal objects. #94851

Automerge-Triggered-By: GH:ericsnowcurrently

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @kumaraditya303 for commit 21ced2f 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

[ericsnowcurrently]

Other than one small thing, LGTM. I suspect we will rip this out once (if) PEP 683 lands. Even then this is a helpful stopgap.

[bedevere-bot]

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.

[ericsnowcurrently]

Thanks for adding the constant! There's a comment to add and then this should be ready to merge.

[ericsnowcurrently]

LGTM

[kumaraditya303]

Thanks for the reviews @ericsnowcurrently!