swh.lister.npm: Add an incremental npm lister
This new lister enables to get only new or updated npm packages since the last listing operation.
As I explained in the task description, the idea would be to use the full npm lister for creating the first batch of oneshot loading tasks for npm packages. Then, use this incremental lister on a regular basis to only get relevant packages to load again.
Related T1378 Closes #1398 (closed)
Migrated from D756 (view on Phabricator)