[views/optimization] Makes has_editable_relations predicate less costly by using generator
The `has_editable_relations` predicate is used to say if the 'modify' action
should appear. To do so, it checks if anything is editable (ie. something in the
attributes, relations or inlined section of the automatic form).
This may be costly since it may have to check several permissions. To optimize
this a bit, this cset turns list into generator so that we'll avoid unnecessary
work as soon as we find a match.