Caching commit hashes

[asamalik]

The generate_modulemd_with_hashes.sh script can generate a modulemd with commit hashes for every component, reflecting the repodata it uses. Doing it this way makes the builds much more reproducible, as we use the same thing we are resolving against

---

The script isn't run as part of the regenerate-everything.sh because it's verry slow.

The script asks Koji for every hash, every time. If it could use some caching, similar to make_modulemd.pl from the https://github.com/fedora-modularity/baseruntime-package-lists repo would make it much faster.

If we fix it, we can generate hashes every time very quickly.