Cannot set store_failures as test modifier for unique, not_null

[jtcohen6]

Describe the bug

Cannot set store_failures config on unique and not_null tests:

  - name: my_model
    columns: 
      - name: id
        tests:
          - not_null:
              store_failures: true # does not take effect

These built-in tests use an optimized codepath for test construction at parse time.

We either missed this in the original PR, or it got lost in the git merge/rebases. It's a super simple fix.

While here, I realized that I think we're not doing unrendered_config quite right. That's a separate issue to look into. (edit: opened #3576)