ci: Improve shared python workflows

[vdusek]

Workflow improvements:

• Update shared workflow input names to snake_case
• Add tests_concurrency input for controlling parallel test execution
• Use @improve-shared-python-workflows branch for testing

Pytest configuration:

• Standardize addopts to "-r a --verbose"
• Remove --verbose from poe task commands (now in addopts)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.41%. Comparing base (1682ff1) to head (e474588).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1680   +/-   ##
=======================================
  Coverage   92.41%   92.41%           
=======================================
  Files         157      157           
  Lines       10482    10482           
=======================================
  Hits         9687     9687           
  Misses        795      795           

Flag	Coverage Δ
unit	92.41% <ø> (ø)

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