Test https-everywhere backend migration
Test fix we land for #40137 (closed). For example, download
10.0a5 and then let the updater download the full mar for the latest update (after #40137 (closed) lands). Confirm the data was migrated successfully. #40137 (comment 2709090) has a suggestion for monitoring the migration, too.
We should run this multiple time because there is a race involved.