Default Map text fields to be longtext (render as textareas)

When working with Map custom inputs, either in Symbols or in Content Models, the default input box is a simple input field. This would probably be fine if the majority of editing on these fields didn't happen in the narrow sidebar, but because that is where the editing happens, it makes it so you can typically see no more than 10 or so characters at a time.

It'd be really nice if these fields were defaulted to render as textareas rather than simple inputs so you could see the full value of the map key:value properties.