fix failing CI, update python versions

[jakkdl]

drop 3.8 testing+support
remove some 3.7 remnants
add 3.13 and 3.14 testing+support
silence pytest-asyncio deprecationwarning
fix typing errors
fix pep8 errors
fix poetry warning

incorporates #271 and #272

this code base would also benefit from running flake8-upgrade (or similar) and replace all imports from typing that can be replaced with standard objects (e.g. List -> list) but I thought this PR was big enough already.

[jakkdl]

ugh, the runners don't have 24.04 + x64 + 3.14. They do have builds for 24.04 + 3.14 with other architectures, and 22.04 + x64 + 3.14.

Up to you if you want to keep it in ci.yml until it's available (presumably they'll have more builds once it exits the beta), remove it, do fancy matrix stuff for the ubuntu version, or whatever. @pgjones

[agronholm]

The setup-python action seems to be missing allow-prereleases: true?

[jakkdl]

Since mypy 1.16 --strict-bytes is enabled by default with --strict, which raised a couple new errors. I opened python-hyper/h2#1305 and python-hyper/h11#186 and widened a few types, but it's likely that a fair amount of the remaining 70-ish type hints, of which ~20 are parameters, using bytes can be widened.

[jakkdl]

@pgjones :)

[jlaine]

This would be great as all PRs currently fail their CI check :)

[pgjones]

Thanks, fixed in 07a7b14