Add run_sync and ensure_async functions

[davidbrochart]

• ensure_async is used in jupyter-client, jupyter-server and nbclient.
• run_sync is used in jupyter-client and nbclient.

See https://github.com/jupyter/nbclient/pull/259.

[davidbrochart]

To be merged after this PR:

• https://github.com/jupyter/jupyter_client/pull/889
• https://github.com/jupyter-server/jupyter_server/pull/1093
• https://github.com/jupyter/nbclient/pull/259

[blink1073]

Mind adding tests?

[blink1073]

@meeseeksdev please backport to 4.x

[lumberbot-app[bot]]

Oops, something went wrong applying the patch ... Please have a look at my logs.

[blink1073]

From the log, it is a merge conflict, but for some reason the bot didn't give the usual message:

2022-11-24T16:33:26.629857+00:00 app[web.1]: hint: To abort and get back to the state before "git cherry-pick",

2022-11-24T16:33:26.629858+00:00 app[web.1]: hint: run "git cherry-pick --abort".'

2022-11-24T16:33:26.629861+00:00 app[web.1]:     [backport] ----

2022-11-24T16:33:26.629863+00:00 app[web.1]:     [backport] 

2022-11-24T16:33:26.629863+00:00 app[web.1]:   stdout: 'Auto-merging jupyter_core/utils/__init__.py

2022-11-24T16:33:26.629865+00:00 app[web.1]: CONFLICT (content): Merge conflict in jupyter_core/utils/__init__.py'

2022-11-24T16:33:26.629920+00:00 app[web.1]:     [backport] ----

[davidbrochart]

I think @fcollonval was having issues with meeseeks lately too.

[Carreau]

Small afer the fact question, why ensure_async(func(param)), which can be problematic if func() can already return an awaitable, and not ensure_asyncfunc(func)(param), that can use inspect.iscoroutinefunction() to make sure func is itself async ?

[davidbrochart]

We just didn't face this situation, but I agree it would have been more generic.