Add pixi support

[olivier-roussel]

Adds Pixi support for developers and CI.
Enables to:

• Have a standard way for a new developer to configure/build the project (homogeneous with other projects) and available on all platforms
• All dependencies stored in one file
• Have an easy way to enable some optional features (e.g. enable some Visp modules, enable python bindings, etc.)
• Have a lock file for a reproducible build in CI (this would replace our conda-based CIs)

TODO:

• base pixi.toml file with build scopes
• optional features for full build scope (TBD)
• lockfile update bot
• pixi-based CI for linux-64 / win-64 / osx-64 / osx-arm64

More info on pixi: https://pixi.sh/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.51%. Comparing base (427354d) to head (d0b292b).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1589      +/-   ##
==========================================
- Coverage   54.53%   54.51%   -0.02%     
==========================================
  Files         442      442              
  Lines       53465    53465              
==========================================
- Hits        29156    29147       -9     
- Misses      24309    24318       +9     

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