Editorial Metadata - new types: dropdown and multiple checkboxes

## Expected/Desired Behavior

Desired behavior for improvements/enhancements: Editorial Metadata: Allow for multiple-choice checkboxes and dropdowns.

Ex:
This post's metadata is being audited to determine if it has supporting materials. The status 1 question within that field could be: Has slides completed, Needs slides completed, Slides not yet created, Slides not needed.

## Actual Behavior

Many checkboxes or other field types are supported, but none that indicate a progression within one choice.

## (Optional) Additional notes

This would be super useful on https://learn.wordpress.org/

The issue does not identify files, tests, or an entry point. Start by locating the existing Editorial Metadata implementation and its supported checkbox field type; done means users can configure and use dropdown and multiple-choice checkbox fields for progression options such as the stated slides statuses.

Written by the indexing model from the issue text.