Separation of concern to restore user and project .fmu from memory

The current restore from memory endpoint automatically restore both user and project .fmu. With the latest `fmu-settings`, we can now call restore to only restore user or project .fmu. Thus, we need to distinguish them, maybe with separate endpoint or special handling in the service logic.

We can also list the restorable files, and if there's no restorable files and we don't need to call restore.