cli.add_forge_now: Open register-lister with sensible defaults

This will ease scheduling of new add-forge-now requests, on:

• staging: this will list a subset of disabled origins once
• production: this will register recurring tasks (full, incremental if any) to list that new forge

This also unifies the previous subcommand schedule-first-visits with the --preset flag.

So, the following would be enough to list appropriately in staging/production:

swh scheduler add-forge-now \
( --preset [production|staging] \ # to enable a pre-defined set of rules )
  register-lister \
    gitea \
    url=https://git.afpy.org/api/v1/

Related to https://gitlab.softwareheritage.org/infra/sysadm-environment/-/issues/4674