uaiohttpclient: parse port instead of hard code 80

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I was getting an error using uaiohttpclient and it was due to it hard coding port 80 for the target host. This PR makes a trivial change to split host:port if present in the URL. I thought it also sensible to update all the yield from to await everywhere and of course preface those functions async. I made a couple of other minor changes which were suggested by ruff and flake8, i.e. a variable l I changed to ln and there was a comment > 80 chars which I wrapped.

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Although trivial, I have changed this PR from 1 commit into 4 separate commits because they are logically distinct changes and this makes it easier to review. I can also easily remove or squash any commits you request.

[dpgeorge]

Thank you, this is a good fix for the port number, and also a nice clean up with the other commits. And thanks also for splitting the commits into logical changes.