[adapters] Use an adapter for serializing entities to a bare python structure which may be used for e.g. JSON export or other and allow to have different serializations for each entity types. Closes #6378035

# re-read ComputedRelation permissions from schema.py now that we're
# able to serialize them
for computedrtype in schema.iter_computed_relations():
    sync_schema_props_perms(computedrtype.type)