Ensure that all lister classes have the same set of mandatory parameters
in their constructors, notably: scheduler, url, instance and credentials.
Add a new test checking listers classes have mandatory parameters declared
in their constructors. The purpose is to avoid deployment issues on staging
or production environment as celery tasks can fail to be executed if mandatory
parameters are not handled by listers.
Reated to swh/infra/sysadm-environment#5030.
In listers collecting artifacts for each package to load, add artifacts
checksums, when that info is available, in parameters sent to loaders
in order to check downloaded artifact integrity.
