CI+Sandbox: Stop using setup.py, instead only use pip

[amotl]

About

A little modernization, preparing to phase out setup.py.

Details

/home/runner/work/grafana-wtf/grafana-wtf/.venv/lib/python3.13/site-packages/setuptools/command/develop.py:41: EasyInstallDeprecationWarning: easy_install command is deprecated.
 /home/runner/work/grafana-wtf/grafana-wtf/.venv/lib/python3.13/site-packages/setuptools/_distutils/cmd.py:66: SetuptoolsDeprecationWarning: setup.py install is deprecated.
!!
        ********************************************************************************
        Please avoid running ``setup.py`` directly.
        Instead, use pypa/build, pypa/installer or other
        standards-based tools.
        See https://blog.ganssle.io/articles/2021/10/setup-py-deprecated.html for details.
        ********************************************************************************
!!

References

• https://github.com/grafana-toolbox/grafana-wtf/actions/runs/11407189355/job/31742761728?pr=147#step:5:25

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.32%. Comparing base (e96bf02) to head (8be698c).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #149   +/-   ##
=======================================
  Coverage   87.32%   87.32%           
=======================================
  Files           9        9           
  Lines        1089     1089           
=======================================
  Hits          951      951           
  Misses        138      138           

Flag	Coverage Δ
unittests	87.32% <ø> (ø)

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