Support drag and drop in event highlights fields

### Problem Statement

You just shipped customisable "event highlights", which are great. However you can only add/remove event highlights from the list, and are unable to re-order them how you want.

In the example above, if I wanted to move "organisation_id" to be after "User", I'd have to remove it and then add it again. It gets a bit complicated if you add loads of fields.

### Solution Brainstorm

Support dragging and dropping the fields

### Product Area

Issues