This removes the nodepool hosts from inventory and all of their jobs
and configuration. Since the zuul-launchers use the "nodepool"
clouds.yaml and associated template variables, those are all renamed
to "zuul".
The corresponding changes (additions of zuul_* variables, not removal
of nodepool_* vars) has been made on bridge.
Change-Id: I7ab28706b2bd20cf4f90b3b45a640fc341976e47
Depends-On: https://review.opendev.org/955235
6f6ae8d6ff