convenience functions for writing RepoData

[pavelzw]

after reworking rattler_index in #1076, i think it would be nice to add some convenience functions to generate the different repodata formats, including:

• repodata.json
• repodata.json.bz2
• repodata.json.zst
• repodata.jlap
• sharded repodata

rattler-index (and conda-mirror, which i'm currently also working on right now) could then use these functions to generate all repodata variants that are supported by pixi/conda/mamba right now.

• we also should support repodata patching feat: Add support for repodata patching in rattler-index, fix silent failures #1129

[baszalmstra]

I dont think we need to support jlap. The CEP never passed and it has been superseded by sharded repodata.