Revert latest changes to ThreadedZMQSocketChannel because they break Qtconsole

[ccordoba12]

• Those changes were done in commit 0057186, released in version 7.3.2.
• They break Qtconsole and hence Spyder, but I checked locally that a simple revert fixes the problem.
• I added the qtconsole test suite here to avoid future breakages.

[ccordoba12]

@blink1073, this is ready for review. As you can see, the Qtconsole test suite passes with these changes (you can check that it dies with Jupyter-client 7.3.3).

Note: I don't know how to fix the MyPy error, so I need help with that.

[blink1073]

Hi @ccordoba12, I think this might be an error in the typings in pyzmq. I added a type ignore for now.

[blink1073]

Thanks very much for adding the qtconsole test!

[blink1073]

Docs failure is unrelated, I'll pick that up in a separate PR.

[ccordoba12]

I think this might be an error in the typings in pyzmq. I added a type ignore for now.

Great! Thanks for your help with that.

Thanks very much for adding the qtconsole test!

No prob. Jupyter-client is critical for us, so that's something we really needed to do (I'll do the same in IPykernel once I have some time).

[blink1073]

I'll cut a release once I merge #804

[davidbrochart]

Thanks @blink1073 and @ccordoba12 for taking care of that.
Something is still not clear to me, is the callback passed to ZMQStream.on_recv an awaitable or not in pyzmq v23.0?
I raised that point in the original PR. Would love some feedback from @minrk.