cli.add_forge_now: Open schedule-first-visits with sensible defaults
This should ease scheduling the first visits for add-forge-now request.
The following would be enough to fetch and schedule the forge just listed (be it in
production or staging):
swh scheduler add-forge-now \
schedule-first-visits \
--visit-type git \
(--visit-type svn \ # if a lister lists multiple kinds of visit, we can mention it )
--lister-name gitea \
--lister-instance-name git.afpy.org \
( --production | --staging ) # to list only enabled | disabled originsRelated to https://gitlab.softwareheritage.org/infra/sysadm-environment/-/issues/4674