[DMN Designer] Remove Stunners Explorer widget from the RHS dock

The DMN Editor has a "Decision Navigator" widget (in the LHS dock) that currently shows the content of the whole DRG however it will also become the DRD explorer too. This duplicates Stunner's default Explorer widget in the RHS dock.

The DMN Editor should have Stunner's default widget removed.

Acceptance Test

• Bpmn still has dock
• Dmn Expand/Colapse properties panel
• Expand/Collapse canvas
• Expand/Collapse left side dock
• Switch editor tabs