Investigate using postgresql ArrayField rather than JSONField for simple, one-dimensional lists of strings

[dralley]

We've got a ton of these: https://github.com/pulp/pulp_python/blob/master/pulp_python/app/models.py#L113-L117

It would be interesting whether ArrayField is more efficient or convenient for this use case. https://docs.djangoproject.com/en/3.2/ref/contrib/postgres/fields/#arrayfield

We should do some research to see if it's a good idea - other plugins may want to adopt it also.