ProjectStorage: Type icons for generated types

There should be some way to set type icons for generated types that do not have .metainfo files whenever such types are detected in file system.

Use case:

• Navigator shows modelNode.typeIcon() for each node. This icon needs to be somehow correctly set for generated types that do not have .metainfo files. Maybe a callback that can be handled somewhere that has access to GeneratedComponentUtils whenever new type is detected?