Add config dependency on migration entity to cron_migration entities

Not sure whether it's a bug or not.

trackleft2 → changed the visibility of the branch 3451525-add-config-dependency to hidden.

trackleft2 → changed the visibility of the branch 2.1.x to hidden.

I think we need to add a post_update function in order to update existing cron migration config entities to add their dependencies.

I've added a post update function that just resaves all of the existing cron migrations on the site in order to recalculate dependencies.