Add edge IDs when they are missing

[caufieldjh]

Some - but not all - transforms do not get assigned edge IDs.
In BFO, for example:

id	subject	predicate	object	category	relation	knowledge_source
	BFO:0000002	biolink:subclass_of	BFO:0000001		rdfs:subClassOf	BFO_relaxed.owl
	BFO:0000003	biolink:subclass_of	BFO:0000001		rdfs:subClassOf	BFO_relaxed.owl
	BFO:0000004	biolink:subclass_of	BFO:0000002		rdfs:subClassOf	BFO_relaxed.owl
	BFO:0000020	biolink:subclass_of	BFO:0000002		rdfs:subClassOf	BFO_relaxed.owl
	BFO:0000031	biolink:subclass_of	BFO:0000002		rdfs:subClassOf	BFO_relaxed.owl

I'm not sure if I had a solution for this in the previous transform process (https://github.com/ncbo/BioPortal-to-KGX/blob/main/bioportal_to_kgx/functions.py) but in KG-OBO, blank edge IDs are assigned a unique ID.