Revert "Revert "Prerender thumbnails at upload time on all wikis except commons""

This reverts commit b9dc5eae9275e2a8330ab1f32c589779b49ef2a2.

Change-Id: I04a211b3ba320b96736c29747f41012140c1427a
Merge "Revert "Revert "Prerender thumbnails at upload time on all wikis except commons"""