Function manifest_from_webc_metadata 

pub(super) fn manifest_from_webc_metadata(
    webc_manifest: &Manifest,
) -> Result<Manifest>

Convert a webc manifest into a Manifest, extracting the package metadata.

Note: only the package metadata (name, version, description, etc.) is extracted; modules, commands, and filesystem mappings are not, because they are already baked into the webc and are not needed to describe the package.