Test coroutine interruption with async client

[davidbrochart]

See jupyterlab/jupyterlab#12194.

It looks like interrupting a cell execution which consists of awaiting a coroutine, e.g.:

import asyncio

async def main():
    await asyncio.sleep(5)

await main()

doesn't take effect immediately, but once the coroutine completes execution. This only happens with an async client. It doesn't happen on the Notebook because I think it uses a blocking client.

[davidbrochart]

Actually it looks more like an ipykernel issue, since akernel stops immediately after interruption.
I tried xeus-python (not raw xeus-python since it doesn't allow awaiting at the top-level), but interrupting such a coroutine leads to the kernel dying.