This reverts the pattern pushed in the main Lister class and defines it specifically in
the listers that were identified as needing it:
- The launchpad lister has just one iterator of origins so this needs to be splitted to have incremental results flushed to the scheduler [1]
- For cgit, it's mostly for instances which returns a high number of results per page (e.g git.eclipse.org, ...). [2]
[1] T2998#57546
[2] T2998#57500
[3] T376#57560