Fill missing authorized projects rows

This MR adds a migration that schedules AuthorizedProjectsWorker jobs for all users where authorized_projects_populated is not set to true. This should solve the problem described in https://gitlab.com/gitlab-org/gitlab-ce/issues/26194.

Regarding the impact, this was tested on GitLab.com and the conclusion was that it should be able to handle this just fine. See https://gitlab.com/gitlab-org/gitlab-ce/issues/26194#note_20997056 for more information.