Speed up finding the reason if its unset

[bdraco]

What do these changes do?

Previously a new enum object had to be created and the reason phase looked up. Since there are a limited number of codes, we can pre-build a dict with all the phases which makes the runtime code much simpler

Are there changes in behavior for the user?

no

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

no

related issue #2779

init request

before

after

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.32%. Comparing base (88f3834) to head (cf902f2).
Report is 1065 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9175   +/-   ##
=======================================
  Coverage   98.31%   98.32%           
=======================================
  Files         107      107           
  Lines       34508    34513    +5     
  Branches     4100     4101    +1     
=======================================
+ Hits        33928    33935    +7     
+ Misses        410      408    -2     
  Partials      170      170           

Flag	Coverage Δ
CI-GHA	98.22% <100.00%> (+<0.01%)	⬆️
OS-Linux	97.88% <100.00%> (+<0.01%)	⬆️
OS-Windows	96.30% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.56% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	97.65% <100.00%> (+<0.01%)	⬆️
Py-3.10.15	97.59% <100.00%> (+<0.01%)	⬆️
Py-3.11.10	97.48% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	97.54% <100.00%> (+<0.01%)	⬆️
Py-3.12.6	97.93% <100.00%> (+<0.01%)	⬆️
Py-3.9.13	97.54% <100.00%> (+<0.01%)	⬆️
Py-3.9.20	97.48% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.16	97.10% <100.00%> (+<0.01%)	⬆️
VM-macos	97.56% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	97.88% <100.00%> (+<0.01%)	⬆️
VM-windows	96.30% <100.00%> (+<0.01%)	⬆️

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[patchback]

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

❌ Failed to cleanly apply 756fae8 on top of patchback/backports/3.10/756fae80b824bf1606235962bd2b460b63da4da0/pr-9175

Backporting merged PR #9175 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/3.10/756fae80b824bf1606235962bd2b460b63da4da0/pr-9175 upstream/3.10

4. Now, cherry-pick PR Speed up finding the reason if its unset #9175 contents into that branch:

   $ git cherry-pick -x 756fae80b824bf1606235962bd2b460b63da4da0

   If it'll yell at you with something like fatal: Commit 756fae80b824bf1606235962bd2b460b63da4da0 is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x 756fae80b824bf1606235962bd2b460b63da4da0

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Speed up finding the reason if its unset #9175 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.10/756fae80b824bf1606235962bd2b460b63da4da0/pr-9175

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: 💚 backport PR created

✅ Backport PR branch: patchback/backports/3.11/756fae80b824bf1606235962bd2b460b63da4da0/pr-9175

Backported as #9213

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