[PR #9454/b20908e backport][3.10] Simplify DNS throttle implementation

[bdraco]

(cherry picked from commit b20908e)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.82%. Comparing base (ee87a04) to head (ef87aab).
Report is 90 commits behind head on 3.10.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             3.10    #9457   +/-   ##
=======================================
  Coverage   97.81%   97.82%           
=======================================
  Files         108      106    -2     
  Lines       34986    35046   +60     
  Branches     4191     4216   +25     
=======================================
+ Hits        34221    34282   +61     
+ Misses        569      568    -1     
  Partials      196      196           

Flag	Coverage Δ
CI-GHA	97.70% <100.00%> (+<0.01%)	⬆️
OS-Linux	97.39% <100.00%> (+<0.01%)	⬆️
OS-Windows	94.93% <100.00%> (+0.01%)	⬆️
OS-macOS	97.09% <100.00%> (+0.01%)	⬆️
Py-3.10.11	96.94% <100.00%> (+0.01%)	⬆️
Py-3.10.15	96.88% <100.00%> (+<0.01%)	⬆️
Py-3.11.10	96.96% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	97.03% <100.00%> (+<0.01%)	⬆️
Py-3.12.7	97.43% <100.00%> (+0.01%)	⬆️
Py-3.13.0	97.41% <100.00%> (+0.01%)	⬆️
Py-3.8.10	94.31% <100.00%> (+0.01%)	⬆️
Py-3.8.18	96.68% <100.00%> (+<0.01%)	⬆️
Py-3.9.13	96.85% <100.00%> (+<0.01%)	⬆️
Py-3.9.20	96.80% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.16	96.40% <100.00%> (+<0.01%)	⬆️
VM-macos	97.09% <100.00%> (+0.01%)	⬆️
VM-ubuntu	97.39% <100.00%> (+<0.01%)	⬆️
VM-windows	94.93% <100.00%> (+0.01%)	⬆️

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