clean up dependency and usages handling in interface files
While reviewing #1480 (closed), it was found that there are corner cases that are not easy to handle.
This task is about fixing TH module reification to reify direct import list, not usages. For this we may need to extend the current
This task also includes cleaning up the comments and code in related areas, to quote simonpj: "we need more precise commentary on the fields of
ModIface. For example, I wonder whether the
mi_usages field could be part of the