feat: implement mirror and oci settings

[wolfv]

This also updates the toml crate because I ran cargo update. Apparently Document is deprecated in favor of DocumentMut.

[pavelzw]

Closes #172

[pavelzw]

could we also add a info or debug message that tells you which mirror you are using in the end?

[ruben-arts]

Testing the examples in the documentation still gives me:

ERROR rattler_repodata_gateway::fetch: error=Request error: HTTP status client error (401 Unauthorized) for url (https://prefix.dev/conda-forge/osx-arm64/repodata.json.zst)
  × failed to fetch repodata from channels
  ├─▶ Request error: HTTP status client error (401 Unauthorized) for url (https://prefix.dev/conda-forge/osx-arm64/repodata.json.zst)
  ╰─▶ HTTP status client error (401 Unauthorized) for url (https://prefix.dev/conda-forge/osx-arm64/repodata.json.zst)

Not sure it is because the website doesn't work or because of the mirror.

Edit: This bug was happening because I didn't have a working token. This is however not correct as it shouldn't error on a broken token while accessing a public channel. @baszalmstra is onto it.

[pavelzw]

Shouldn't these be dependent on the config?

[pavelzw]

Ah nvm this should be done in #1015