gitlab: Add test on incremental implementation
Note that the current implementation will start back the new visit from the last next_page link seen (that's what is stored in the lister state to avoid computing back the url). This means that this page will be seen at least 2 times, on the first visit and on the next. This should not pose any problems as the listing is idempotent.
Related to #2987 (closed) Depends on D4930
Migrated from D4932 (view on Phabricator)