Refs #34118 -- Adopted asgiref coroutine detection shims.

[carltongibson]

ticket-34118 Python 3.12 compatibility.

Refs python/cpython#99247
Refs django/asgiref#360

This PR requires at least the asgiref branch to test.

Python 3.12 deprecates asyncio.iscoroutinefunction() as an alias for
inspect.iscoroutinefunction(), whilst also removing the _is_coroutine marker.
The latter is replaced with the inspect.markcoroutinefunction decorator.
Until 3.12 is the minimum supported Python version, use the shims from asgiref.sync.

[andrewgodwin]

👍

[carltongibson]

Rebased and updated the asgiref dependency for 3.6.0, which has the shims in place.

[felixxm]

@carltongibson Thanks 👍

[carltongibson]

Thanks @felixxm 🚀