feat: as graphql _groupBy user I can also use non-ontology tables for aggregation

[mswertz]

Is your feature request related to a problem? Please describe. In dashboards we want to enable group by on other fields.

Describe the solution you'd like

• [ ] expand graphql api to allow group by fields to of all types (remove the ontology filter)
• [ ] check that the SqlQuery indeed handles those fields as group by fields
• [ ] check and fix tests that might not cover these (so: refs, ref_array and primitive types/arrays)

Describe alternatives you've considered We discussed that in long term we would like to merge _agg and _groupBy api

Additional context probably start here https://github.com/molgenis/molgenis-emx2/blob/4081ec3f12881cb39d323d9cdd9a3216f594b775/backend/molgenis-emx2-graphql/src/main/java/org/molgenis/emx2/graphql/GraphqlTableFieldFactory.java#L321