bpo-43232: Prohibit previously deprecated operations on TransportSocket

[illia-v]

Probably the warning should be updated in Python 3.8 and Python 3.9 to avoid confusion ("will be prohibited in asyncio 3.9" -> "will be prohibited in Python 3.10").

https://bugs.python.org/issue43232

[illia-v]

BTW, I didn't document the change in What's New, because it looks like the class is pretty low-level. If it should be documented there, please let me know in what section: neither "Deprecated" nor "Removed" seem to suite.

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[serhiy-storchaka]

Instead of explicitly raising RuntimeError, just remove the corresponding methods.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[illia-v]

I have made the requested changes; please review again

[bedevere-bot]

Thanks for making the requested changes!

@serhiy-storchaka: please review the changes made to this pull request.

[sbourdeauducq]

Why was ioctl removed? How do we set up TCP keepalive on Windows without it?

[serhiy-storchaka]

The warning was added in 3.8 (see #81208), 4 years ago. This PR was merged 2 years ago. Please open a new issue for your use case.