ci: Replace PAPR with CoreOS CI

ci: Replace PAPR with CoreOS CI

Move the alternative builds into the Jenkinsfile.

Update it to do a FCOS build + kola run.

We drop the flatpak/rpm-ostree runs for now; the former
will needs some work to do the automatic virt bits.  The
latter I think we can circle back to when we e.g. figure
out how to include rpm-ostree's tests in kola runs.