Enhancement: UI support for converting a field to add / edit array values

* There can a UI toggle in the column to convert a text field to accept array values.

* While editing an array field, the UI can look like this:

Currently, we don't support this - refer to the screenshot here:

No files, tests, or entry points are named. Start by locating the existing column and field-editing UI, then compare its text-field behavior with the two linked screenshots; done means a column toggle enables array values and array fields can be added and edited through the intended UI.

Written by the indexing model from the issue text.