Add rule to detect potential bug caused by unheld references to asyncio.create_task

Feature

Hi there,

I wanted to suggest adding a rule to MyPy to help detect a potential bug that can occur when using asyncio.create_task. If a developer doesn't hold a reference to the task object returned by create_task, the task may disappear without warning when Python runs garbage collection. This can lead to unpredictable failures in the code, which can be extremely difficult to debug.

References:
https://textual.textualize.io/blog/2023/02/11/the-heisenbug-lurking-in-your-async-code/
https://news.ycombinator.com/item?id=34754276

Pitch

I think adding a rule to MyPy that flags code which creates an asyncio task but doesn't hold a reference to it would be very helpful in preventing this bug from occurring. It would alert developers to the fact that they need to make sure they're holding a reference to the task object if they want to avoid this problem.

Beginne mit der Überprüfung von mypy’s bestehender Behandlung von asyncio.create_task und der verknüpften Berichte, in denen Aufgaben beschrieben werden, die nicht gehalten werden. Lege fest, welche Muster nicht gehaltener Referenzen die vorgeschlagene Regel melden sollte, wie Diagnosen erscheinen sollten und welche Testfälle belegen, dass die Regel vollständig ist.