Show numerical IDs next to workflow actions when editing a behaviour condition

In the previous Behaviours UI, when you were creating/editing a condition for a behaviour with a guide workflow, the Workflow Action dropdown would show the numerical ID of each action, parenthesised, after the action's name. This was useful for distinguishing identically-named actions in the same workflow.

In the new UI, only the name is shown. We should reintroduce the old approach.