Refactor to return packaged resource names

### What needs to get done

The `pack` command in the package service currently returns a list of packaged artifacts, but In order to generate environment variables for resource files it should also return the resource names (or maybe fill a map passed as an optional argument). Refactor pack to obtain this information, and after that the `resource_map` property can be removed.

### Why it needs to get done

The testing setup requires environment variables with resource names pointing to resource files.

Start with the package service's `pack` command and trace how it currently returns packaged artifacts and uses the `resource_map` property. Decide how resource names should be returned, remove the obsolete property, and verify that the testing setup can generate environment variables pointing to resource files.

Written by the indexing model from the issue text.