ENG-1358 - Hide canvas relation when reified relations enabled (#759)

* Hide canvas relation when reified relations enabled

* Add support for reified relations in DiscourseRelationConfigPanel

- Introduced a new setting to toggle the use of reified relations.
- Updated the component to conditionally render the relation editing interface based on the reified relations setting.
- Adjusted the behavior of the loadCytoscape function to prevent loading when reified relations are enabled.

* Refactor DiscourseRelationConfigPanel to improve node and edge handling

- Ensure cyRef.current is defined before accessing nodes and edges.
- Simplify unsavedChanges and setSource/setDestination calls in MenuItemSelect components.

Author: mdroidian