[IMP] field: compute transitive dependencies over non-stored fields

In other words, when a field F depends on a non-stored field G, it also depends
on G's dependencies.  This guarantees that whenever a dependency of G is
modified, F will be invalidated and marked to recompute (if necessary).

The transitive closure of dependencies is not computed over stored fields.
Anyway stored fields already trigger the recomputation of their dependent
fields during their recomputation.  The performance impact on the loading of a
registry is negligible (less than 1%), and the increase of recomputation
triggers is small (less than 10%).