fixes #7952

see in particular #7952 (comment)
> So the issue is with the aiorpcx monkey patch in util.py, as it
> relies on side-effecting the asyncio.Task, and it patches Task.cancel.
> However, aiohttp also uses Task.cancel for its own timeouting of the
> http request, with the same Task object, and this confuses timeout_after.
> Ultimately FxThread.run exits.

related kyuupichan/aiorpcX#47

---

note: I am not content at all with this monkey-patching approach,
but at the same time I don't see how to properly fix this handling all
edge-cases in aiorpcx.

python 3.11 is finally adding an implementation of TaskGroup [0] and
an async timeout context manager [1] in the asyncio module of the stdlib.
Looking at the implementations, they look unfeasible to backport:
much of the implementation of asyncio.Task had to be changed for them
to work, and TaskGroup in particular relies on the new ExceptionGroups.
Some of these edge cases we are battling with aiorpcx.curio look
difficult to fix without those stdlib changes...
Anyway, when we bump the min python to 3.11, I look forward to switching
to that code instead, and ripping this stuff out.

[0]: https://docs.python.org/3.11/library/asyncio-task.html#task-groups
[1]: https://docs.python.org/3.11/library/asyncio-task.html#asyncio.timeout