Option to execute Background Migrations immediately

As an GitLab self-hosted administrator, who can't update to each version as soon as it is released, I often have to upgrade to some intermediate versions according to the upgrade plan. The background migrations significantly increase the total time required.

I am currently upgrading from 15.3.x to 15.7.x, which means I need to migrate to 15.4.0 first. Unfortunately, 15.4.0 contains several background migrations, which take several hours due to the delay interval, so I have to wait several hours before I can start the upgrade to 15.7.2. In my small setup, I'm able to use migration downtimes, so a performance decrease due to background migrations doesn't matter. Therefore, I'd like to be able to force the execution of the background migrations.