test: generate snapshots for all Python versions

[noirbizarre]

Description

@bearomorphism I heard you so here's my proposal.

poetry test:all now use tox-uv to install required Python versions. Contributors have nothing to install on their own. Double benefit: dependencies installation will now be faster when running poetry test:all

Added a python_version fixture creating a single parametrize parameter with the current Python version in the form major.minor:

• tests requiring it will run with the current version only and have their snapshots name including the Python version
• the test:all suite will run this over every Python version with a version-specific snapshot

Added a poetry test:regen command that will in parallel:

• regenerate all snapshots but those depending on the Python version using the current Python interpreter
• regenerate snapshots depending on the Python version using tox

Update the contributing guide to document this.

Checklist

• I have read the contributing guidelines

Code Changes

• adds tox-uv dependency
• adds a poetry test:regen command and adds it to the contributing guide
• adds a python_version fixture and uses it in test_common_command.py
• regenerate the snapshots for all Python versions

Documentation Changes

Update the CONTRIBUTING.md

Expected Behavior

• it's easy and simple to test against all version
• test suite supports Python version dependant snapshotting
• regenerating snapshot is easy

Steps to Test This Pull Request

Supersedes #1741

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.84%. Comparing base (120d514) to head (c1effb1).
⚠️ Report is 899 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1748      +/-   ##
==========================================
+ Coverage   97.33%   97.84%   +0.51%     
==========================================
  Files          42       60      +18     
  Lines        2104     2604     +500     
==========================================
+ Hits         2048     2548     +500     
  Misses         56       56              

Flag	Coverage Δ
unittests	97.84% <ø> (+0.51%)	⬆️

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[bearomorphism]

Thanks 🙇 will review it later today.