packagist: Yield pages of origins to regularly record origins

Instead of sending one page with all origins listed which is britle.
When something goes wrong during the listing, the lister currently records nothing.

swh/lister/pattern.py

@@ -356,6 +356,7 @@ class Lister(Generic[StateType, PageType]):
                 else:
                     logger.warning("Skipping invalid origin: %s", origin.url)
 
+            logger.debug("Record valid %s origins in the scheduler", len(valid_origins))
             ret = self.scheduler.record_listed_origins(valid_origins)
             recorded_origins.extend(origin.url for origin in ret)