Because when this is not a simplified profile, we don't want the "auto-deletion"
behaviour, ie deleting the data object when its reference is deleted.

But since we still want this for simplified profiles, reimplement this behaviour
using hook+op.

Removing composite marker also implies to add/change some setup in various
places controlled by the SEDA compound graph, which only consider composite
relation. Add individual explanation as comment for posterity. At some point it
would probably be desirable to allow *additional relations to follow* in the
compound graph (we can only specify relations to filter out for now).

Closes #17113413