Publish `pixi_config` as crate

[pavelzw]

We are planning to use pixi_config as a crate in rattler-build (prefix-dev/rattler-build#1563) as well as in pixi-pack (Quantco/pixi-pack#136).
Would be nice to have this package available as a crate s.t. we can use it in those tools without needing git for it

[Hofer-Julian]

Agreed, let's publish pixi_config and others with release_plz

[ruben-arts]

Quick side though would it be valuable to move stuff like this to the conda-org and try to make it more "conda org" like instead of prefix focussed? There is no value to us to keep this to ourself IMO.

[wolfv]

I think moving this configuration to the rattler crate and having a way to extend it with pixi specific configuration options would be good in the long run.

Things like mirror configuration etc. - would be good to have in multiple places. As well as the logic to override things.

[pavelzw]

obsolete with conda/rattler#1322