Guard more than one workflow transition with a single approval request type

Problem/Motivation

If a workflow state has more than one transition to a subsequent state which requires approval, one must currently configure multiple approval types for each transition. This means that one may need to request two different review types from the same approving user, even though that user is reviewing the current, single state of the workspace.

To prevent that unintuitive behavior, an approval type should be able to guard multiple transitions.

Data model changes

This will require an update to the config entity schema.