Work items - Add "Duplicate" relationship types to linked items

Summary

Historically when using /duplicate the item gets linked in the badge as a duplicate, then again in the linked items as a related item. This creates two different relationship types, which is confusing; further the linked item is more visible, but less clear in its relationship (related vs duplicate of).

With the addition of a status field we want to move away from using the duplicated badge and instead rely solely on status (duplicate) and linked items to convey this. This also enables us to bring the "mark as duplicate" function into the UI, as it's undesirable to have quick action-only features in most cases.

Duplicate relationship types are very common in similar products, and will help round out our link feature in a more predictable manner.

Proposal

1. Add two new relationship types — "duplicates" and "is duplicated by"
   1. To accommodate these additional options, move relationship type to a dropdown.
2. When either duplicated option is selected, show a note that the duplicate items will be closed.
3. When saving a duplicate relationship, save the linked item and...
   1. Apply the default duplicate status to the duplicate work item (if using "duplicates" , this item; if using "is duplicated by", the selected item)
   2. Close the item (or allow it to close automatically via status)
   3. Show a single note in the system notes "marked this item as duplicated by <reference>" or "marked this item as a duplicate of <reference>, set the status to <Duplicate>, and closed"
      1. If necessary system notes can be broken into 2 or 3 distinct events.