Autofix should move custom configs under generic tests under meta

[venkaa28]

This

- name: <any model>
    columns:
      - name: <any column>
        tests:
          - unique:
              config:
                  error_message: 'here is my message'

should become

- name: <any model>
    columns:
      - name: <any column>
        tests:
          - unique:
              config:
                  meta:
                    error_message: 'here is my message'

If a config value is a custom config, it should be moved under meta.