Use PEP 658 metadata download to speed up builds #360
Description
PEP 658 specifies that a Python Package Index can provide the package metadata as a separate file. This allows clients to inspect a pacakge metadata w/o downloading an entire wheel file. I have a hunch that this approach may speed up Fromager's dependency resolution.
We could also store a metadata file next to the wheel file in our local directory tree. add_extra_metadata_to_wheels unpacks the wheel anyway and could copy the METADATA file, too. The file can be used to inspect the metadata of a wheel without unpacking it. GitLab's PyPI does not serve metadata. We could upload the metadata with the wheels, too.