test: Fix data tests

[saraburns1]

Fixing and updating data tests in preparation of adding unit tests

1. Added new 'acceptable_values_xapi' test to run on models that don't exist in the target schema (reporting)
2. Update 'tests' property to 'data_tests' per dbt documentation

[bmtcril]

Thanks for the fixes! It looks like we're not actually running tests as part of CI right now, can you add another step to the workflow? https://github.com/openedx/aspects-dbt/blob/main/.github/workflows/coverage.yml

I think we just need to add this before the "Check docs coverage" step:

      - name: Check dbt tests
        run: |
          dbt run
          dbt test