[Backport maintenance/3.3.x] Ignore leading underscores in private methods for camelCase style

[github-actions]

Backport 5c6950c from #10228.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.84%. Comparing base (f0e4e42) to head (1468e15).
Report is 26 commits behind head on maintenance/3.3.x.

Additional details and impacted files

@@                Coverage Diff                 @@
##           maintenance/3.3.x   #10229   +/-   ##
==================================================
  Coverage              95.84%   95.84%           
==================================================
  Files                    174      174           
  Lines                  18980    18980           
==================================================
  Hits                   18191    18191           
  Misses                   789      789           

Files with missing lines	Coverage Δ
pylint/checkers/base/name_checker/naming_style.py	100.00% <100.00%> (ø)

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