Support pixi for environment management

[jhkennedy]

Currently, our reusable actions that use a Python environment assume it's a conda-mamba environment. We should either:

1. add pixi versions of these actions
2. cut over to using pixi instead of mamba/conda for these actions
3. provide some way of selecting which way to set up the environment

(1) is easiest/fastest but leads to lots of duplication, (2) is drastic and forces every repo to update to pixi and (3) is probably needlessly complicated, so (1) probably makes the most sense.

[cmarshak]

resuable ruff is failing when I remove the environment.yml file