asyncore: improve bytes handling

[sobolevn]

Source: https://github.com/python/cpython/blob/7ea10567afe38e7770e82b4642c0b01659acaad5/Lib/asyncore.py

asyncore.send calls socket.send: https://github.com/python/cpython/blob/7ea10567afe38e7770e82b4642c0b01659acaad5/Lib/asyncore.py#L363

[AlexWaygood]

I don't really want to spend my time reviewing a PR like this for a module that's long-deprecated and about to be removed :(

Same goes for #9035

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[sobolevn]

Yeah, I can totally understand, sometimes I feel this too!
(I even have a backlog of things to review) 😆

But, since typeshed still supports >=3.7, people are and will still use these modules.
This is why I even bothered creating this PR.

Maybe someone else will review it! If you feel like it, closing these two PRs is always an option.

[AlexWaygood]

Yeah, to be clear — I've no objections to other maintainers reviewing and merging this if they want to :)