test: generate snapshots for all Python versions

[noirbizarre]

Description

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

poe 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 poe 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 poe 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 poe 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 97.92%. Comparing base (548621c) to head (ae8e277).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1748   +/-   ##
=======================================
  Coverage   97.92%   97.92%           
=======================================
  Files          60       60           
  Lines        2604     2604           
=======================================
  Hits         2550     2550           
  Misses         54       54           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[bearomorphism]

Thanks 🙇 will review it later today.

[noirbizarre]

PR updated to solve conflicts with the uv switch.