Add support for Python 3.10

[hugovk]

What do these changes do?

Add support for Python 3.10: Trove classifier and create binary wheels for 3.10.

Are there changes in behavior for the user?

No.

Related issue number

No, a follow on from PR #5927.

Checklist

• I think the code is well written
• [n/a] 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
  • ensure type is one of the following:
    • .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."

[webknjaz]

Thank you!

[codecov]

Codecov Report

Merging #6079 (ba1fdea) into master (9723abf) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #6079   +/-   ##
=======================================
  Coverage   93.31%   93.31%           
=======================================
  Files         102      102           
  Lines       30062    30062           
  Branches     2690     2690           
=======================================
  Hits        28053    28053           
  Misses       1833     1833           
  Partials      176      176           

Flag	Coverage Δ
unit	93.24% <ø> (ø)

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[patchback]

Backport to 3.8: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply 02bb200 on top of patchback/backports/3.8/02bb2009cda3814c5cbaddc5b4a466bd0067dbdc/pr-6079

Backporting merged PR #6079 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.8/02bb2009cda3814c5cbaddc5b4a466bd0067dbdc/pr-6079 upstream/3.8

4. Now, cherry-pick PR Add support for Python 3.10 #6079 contents into that branch:

   $ git cherry-pick -x 02bb2009cda3814c5cbaddc5b4a466bd0067dbdc

   If it'll yell at you with something like fatal: Commit 02bb2009cda3814c5cbaddc5b4a466bd0067dbdc is a merge but no -m option was given., add -m 1 as follows intead:

   $ git cherry-pick -m1 -x 02bb2009cda3814c5cbaddc5b4a466bd0067dbdc

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Add support for Python 3.10 #6079 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.8/02bb2009cda3814c5cbaddc5b4a466bd0067dbdc/pr-6079

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[aio-libs-github-bot]

💔 Backport was not successful

The PR was attempted backported to the following branches:

• ❌ 3.8: Commit could not be cherrypicked due to conflicts

[patchback]

Backport to 3.8: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply 02bb200 on top of patchback/backports/3.8/02bb2009cda3814c5cbaddc5b4a466bd0067dbdc/pr-6079

Backporting merged PR #6079 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.8/02bb2009cda3814c5cbaddc5b4a466bd0067dbdc/pr-6079 upstream/3.8

4. Now, cherry-pick PR Add support for Python 3.10 #6079 contents into that branch:

   $ git cherry-pick -x 02bb2009cda3814c5cbaddc5b4a466bd0067dbdc

   If it'll yell at you with something like fatal: Commit 02bb2009cda3814c5cbaddc5b4a466bd0067dbdc is a merge but no -m option was given., add -m 1 as follows intead:

   $ git cherry-pick -m1 -x 02bb2009cda3814c5cbaddc5b4a466bd0067dbdc

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Add support for Python 3.10 #6079 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.8/02bb2009cda3814c5cbaddc5b4a466bd0067dbdc/pr-6079

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[patchback]

Backport to 3.8: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply 02bb200 on top of patchback/backports/3.8/02bb2009cda3814c5cbaddc5b4a466bd0067dbdc/pr-6079

Backporting merged PR #6079 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.8/02bb2009cda3814c5cbaddc5b4a466bd0067dbdc/pr-6079 upstream/3.8

4. Now, cherry-pick PR Add support for Python 3.10 #6079 contents into that branch:

   $ git cherry-pick -x 02bb2009cda3814c5cbaddc5b4a466bd0067dbdc

   If it'll yell at you with something like fatal: Commit 02bb2009cda3814c5cbaddc5b4a466bd0067dbdc is a merge but no -m option was given., add -m 1 as follows intead:

   $ git cherry-pick -m1 -x 02bb2009cda3814c5cbaddc5b4a466bd0067dbdc

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Add support for Python 3.10 #6079 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.8/02bb2009cda3814c5cbaddc5b4a466bd0067dbdc/pr-6079

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.