Allow passing a custom loop setup function instead of None

[gnir-work]

Summary

Support passing a custom IOLoop setup function in order to support running uvicorn in custom ioloop implementation other that the default and uvloop.

For example this feature will allow using this monitored IOLoop inside uvicorn applications :)

Link to discussions thread - #2256

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.

[Kludex]

@gnir-work I don't want to have 2 similar parameters. I'd prefer us to go with this approach: https://github.com/encode/uvicorn/pull/2130/files (which turns the --loop into your --loop-setup.

If you want to move this forward, the best approach would be to continue that PR - fixing the pipeline, etc.

[hxnir]

No problem :)
Just a quick question - How should I go about it? Should I fork the graingert:uvicorn repo and open another PR?
I can also update the current diff to be in the same spirit as the PR you mentioned

[Kludex]

I would add a remote on his repo, get the branch, and push to your fork, and then create a PR.

[gnir-work]

Closing this PR in favor of #2435.
Will update it from draft to open as soon as everything is passing :)