We need to make it easier to update the bootloader on these variants
because unlike on traditional systems, it's not updated automatically
with the rest of the system. Add bootupd for that.

This would allow fixing issues like:
- https://github.com/coreos/rpm-ostree/issues/3715
- https://github.com/fedora-silverblue/issue-tracker/issues/120#issuecomment-979268679

It won't be enabled by default and as mentioned in that comment requires
work in Anaconda to be seamless. But at least with this users should be
able to adopt and update:

https://github.com/coreos/bootupd/blob/main/README-design.md

See also the tracker issue where we did this for Fedora CoreOS:

https://github.com/coreos/fedora-coreos-tracker/issues/510