Hook up listers implemented with the new pattern to the CLI

We stop depending on the ListerBase implementation. The main hoop we're jumping
through is the config override mechanism in swh.lister.get_lister, as it's
really specifc to the ListerBase override_config argument, which is dropped in
pattern.Lister (in favor of explicit arguments at lister instantiation).

We implement a small shim in swh.lister.pattern.Lister to give
backwards-compatibility for the new pattern to get_lister.

This generic configuration override mechanism will probably be completely
removed when the configuration mechanism is reworked. We'll see.