Add pixi support

[jorisv]

This PR add Pixi support for developer and CI.

This aims to have:

• A standard way to new developer to configure/build the project
• All dependencies stored in one file
• A way to easily know optional dependencies
• A lock file to have a more reproducible build in CI
• Overcome the conda cxx-compiler package CXXFLAGS issue
  • https://github.com/conda-forge/conda-forge.github.io/issues/2002
  • https://github.com/stack-of-tasks/pinocchio/issues/2449)

Bonus:

• Fix build without octomap

TODO:

• [x] pixi.toml
• [x] CI
• [x] README.md
• [x] lockfile update bot

[jorisv]

Windows fail are normal, it will be solved by https://github.com/coal-library/coal/pull/630

[jorisv]

https://github.com/coal-library/coal/pull/630 must be merged before this PR