[NO-ISSUE][GRAPHIX] Fixing serialization error for requirements.

Marking the following as serializable (so as to properly send messages
to the metadata node):
- IEntityRequirements
- DependencyIdentifier
- EdgeDescriptor
- ElementLabel

Change-Id: Ia9718d56ef5e1d7dbc80a16e6df0cc67ef689f11
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/asterixdb-graph/+/16603
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Glenn Galvizo <ggalvizo@uci.edu>