[PR #9207/970c5d9 backport][3.11] add proxy and proxy_auth variables to ClientSession.__init__

[meshya]

(cherry picked from commit 970c5d9)

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• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.80%. Comparing base (ac48753) to head (f289444).
Report is 2 commits behind head on 3.11.

Additional details and impacted files

@@           Coverage Diff           @@
##             3.11    #9331   +/-   ##
=======================================
  Coverage   97.80%   97.80%           
=======================================
  Files         108      108           
  Lines       35070    35099   +29     
  Branches     4187     4191    +4     
=======================================
+ Hits        34299    34328   +29     
  Misses        574      574           
  Partials      197      197           

Flag	Coverage Δ
CI-GHA	97.68% <100.00%> (+<0.01%)	⬆️
OS-Linux	97.36% <100.00%> (+<0.01%)	⬆️
OS-Windows	94.87% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.06% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	96.92% <100.00%> (+<0.01%)	⬆️
Py-3.10.15	96.86% <100.00%> (+<0.01%)	⬆️
Py-3.11.10	96.94% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	97.00% <100.00%> (+<0.01%)	⬆️
Py-3.12.6	97.40% <100.00%> (+<0.01%)	⬆️
Py-3.13.0-rc.2	97.38% <100.00%> (+<0.01%)	⬆️
Py-3.9.13	96.84% <100.00%> (+<0.01%)	⬆️
Py-3.9.20	96.78% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.16	96.38% <100.00%> (+<0.01%)	⬆️
VM-macos	97.06% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	97.36% <100.00%> (+<0.01%)	⬆️
VM-windows	94.87% <100.00%> (+<0.01%)	⬆️

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