Simplify DNS throttle implementation

[bdraco]

What do these changes do?

Simplify DNS throttle implementation

When testing #9447 I found there were so many race opportunities that it made sense to refactor the code to reduce the chance for races and make it quite a bit simpler.

This should also improve the performance a bit when we have a thundering herd backing up waiting for the resolver as they no longer need to create tasks and we only need a single task for the resolution that is happening to be able to shield it from cancellation.

Are there changes in behavior for the user?

no

Is it a substantial burden for the maintainers to support this?

no

likely fixes #3431

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.59%. Comparing base (216e082) to head (040e6b1).
Report is 657 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9454   +/-   ##
=======================================
  Coverage   98.58%   98.59%           
=======================================
  Files         107      105    -2     
  Lines       35026    35083   +57     
  Branches     4151     4176   +25     
=======================================
+ Hits        34531    34589   +58     
+ Misses        330      329    -1     
  Partials      165      165           

Flag	Coverage Δ
CI-GHA	98.47% <100.00%> (+<0.01%)	⬆️
OS-Linux	98.14% <100.00%> (+<0.01%)	⬆️
OS-Windows	96.53% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.83% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	97.70% <100.00%> (+<0.01%)	⬆️
Py-3.10.15	97.63% <100.00%> (+<0.01%)	⬆️
Py-3.11.10	97.70% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	97.77% <100.00%> (-0.01%)	⬇️
Py-3.12.7	98.19% <98.70%> (+<0.01%)	⬆️
Py-3.13.0	98.17% <98.70%> (+<0.01%)	⬆️
Py-3.9.13	97.60% <100.00%> (+<0.01%)	⬆️
Py-3.9.20	97.53% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.16	97.16% <100.00%> (+<0.01%)	⬆️
VM-macos	97.83% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	98.14% <100.00%> (+<0.01%)	⬆️
VM-windows	96.53% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[bdraco]

The shielding is preventing the cancellation which prevents the timeout from working as well

nevermind , bad test on my part

[bdraco]

works fine in production.

Lot more coverage now as well

[patchback]

Backport to 3.10: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply b20908e on top of patchback/backports/3.10/b20908e531ff349545cff5e90de24975bc27afda/pr-9454

Backporting merged PR #9454 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/3.10/b20908e531ff349545cff5e90de24975bc27afda/pr-9454 upstream/3.10

4. Now, cherry-pick PR Simplify DNS throttle implementation #9454 contents into that branch:

   $ git cherry-pick -x b20908e531ff349545cff5e90de24975bc27afda

   If it'll yell at you with something like fatal: Commit b20908e531ff349545cff5e90de24975bc27afda is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x b20908e531ff349545cff5e90de24975bc27afda

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Simplify DNS throttle implementation #9454 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.10/b20908e531ff349545cff5e90de24975bc27afda/pr-9454

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 3.11: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply b20908e on top of patchback/backports/3.11/b20908e531ff349545cff5e90de24975bc27afda/pr-9454

Backporting merged PR #9454 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/3.11/b20908e531ff349545cff5e90de24975bc27afda/pr-9454 upstream/3.11

4. Now, cherry-pick PR Simplify DNS throttle implementation #9454 contents into that branch:

   $ git cherry-pick -x b20908e531ff349545cff5e90de24975bc27afda

   If it'll yell at you with something like fatal: Commit b20908e531ff349545cff5e90de24975bc27afda is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x b20908e531ff349545cff5e90de24975bc27afda

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Simplify DNS throttle implementation #9454 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.11/b20908e531ff349545cff5e90de24975bc27afda/pr-9454

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.