Pixi migration

[YooSunYoung]

Should we use pixi for all our packages, not just ess* packages?

This is the overview of the packages who uses tox or pixi.

Dev Tool	Packages
tox	plopp, esslivedata, copier_template, scippneutron, scipp, mplcanvas, tof, chexus, sciline, cyclebane, scippnexus
pixi	ess*, scitiff

[nvaytet]

What problem are we solving by moving to pixi? Does it make some things easier? Does it make some parts faster?

[jl-wynen]

It makes tooling uniform. We only have to remember one set of commands.

[jl-wynen]

For ScippNeutron, it would simplify the setup because we currently have a hybrid Conda / PyPI setup to support Mantid but still lock dependencies with pip-compile.

[nvaytet]

How much could be done just in the copier template and how much manual work would be left in each package?

An alternative is to move more stuff into the monorepo? The we get pixi for free...