[backport][3.8][PR#5494] Release all forgotten resources in tests

[webknjaz]

What do these changes do?

Ever since pytest got updated to v6.2, it started emitting resource
warnings under new Pythons 3.8+ which results in a failed status.

This change addresses this issue by properly most of the resources
so they don't even appear and ignoring the rest in cases of race
conditions and other cases that are hard to track down.

Are there changes in behavior for the user?

No.

Related issue number

N/A

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
  • The format is <Name> <Surname>.
  • Please keep alphabetical order, the file is sorted by names.
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> for example (588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the pr
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    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."

[luckydenis]

Good afternoon. Maybe it's better to use a context manager for the session?

async with aiohttp.ClientSession(loop=loop) as session:
    assert session.version == aiohttp.HttpVersion11

[webknjaz]

Yes, it's better in general but I wanted to keep the patch as small as possible. Besides, if this fails in tests, we'll notice it and if the test succeeds, it does not really matter if an async CM was used or a regular close was called.

Besides, it's a backport PR, it should be kept as close to the original one as possible.

I'm more concerned about all the warnings that I failed to fix and had to ignore for now because they are either flaky or it is unclear what causes them.

That said, feel free to contribute improvements. I have a lot on my plate so I've only made a bare minimum of the changes necessary to get the new pytest up and running. Strictly speaking, I could just fill the config with ignores but I've made an extra effort to improve things which required substantially more involvement than one would expect at glance.

[webknjaz]

Superseded by #6104.