View/Edit Enum Values

It would be nice to be able to view/edit enum values in the same way that we can view tables and edit their rows. As of right now, the only way (that I'm aware of) to view enum options is to find a row that has an enum popup picker and check them there.

Start by reviewing how Postico currently exposes enum options through row-editing popups. Trace the existing table and row editing flow and PostgreSQL enum handling; done means users can view and edit enum values directly rather than finding a row that uses them.

Written by the indexing model from the issue text.