It’s not a service. It’s a configuration of the packages. For example, if Package A must be loaded before Package B, then on the package Settings tab in the 'Package dependencies", you specify Package A as the the package and . as the version. The package loader will ensure that Package A loads before Package B.
In the attached screen shot, WmART is guaranteed to be loaded before the AxAdapter package is loaded. One can chain these dependencies together but you’ll want to be cautious about two things: 1) circular dependencies; 2) putting dependencies in place when package loading order doesn’t matter–when a package is reloaded using Administrator, all package that are dependents are also reloaded. Thus, if you have general purpose package like MyPublic that has lots of common services used by lots of packages, you probably don’t want to add MyPublic as a dependency in all those packages. That’s because any reload of MyPublic will cause all dependent packages to reload–which might effectively be the same as an IS restart.