Describe the bug

Originally, @asvetlov intended to delete any use of attrs from aiohttp 4.0+ series via #5284. He dropped it from the runtime deps too.

But there are some places that still rely on attrs meaning that this will cause failures in runtime because of the missing dep. The tests currently succeed because attrs is listed as a test dep.

One place where it's used is

To Reproduce

pip install the recent master w/o the test deps and it should fail

Expected behavior

aiohttp shouldn't rely on deps not declared in the metadata.

Logs/tracebacks

N/A

Python Version

$ python --version

aiohttp Version

$ python -m pip show aiohttp

multidict Version

$ python -m pip show multidict

yarl Version

$ python -m pip show yarl

OS

N/A

Related component

Server

Additional context

No response

Code of Conduct

• I agree to follow the aio-libs Code of Conduct