GLSP-1166 Fix dependency injection cycle in selection service

[tortmayr]

Avoid binding of SelectionService as IModelRootListner. Instead directly inject theCommandStack into SelectionService and manually register itself as IGModelRootListener. This avoids a circular dependency injection if any of the SelectionListners wants to inject the ActionDispatcher.

Can be tested e.g. by creating a SelectionListener that injects the action dispatcher:

@injectable()
export class MySelectionListener implements ISelectionListener {
    @inject(TYPES.IActionDispatcher)
    protected actionDispatcher: ActionDispatcher;

    selectionChanged(root: Readonly<GModelRoot>, selectedElements: string[], deselectedElements?: string[] | undefined): void {
        console.log('Selection changed: ' + selectedElements);
    }
}

// bind it in the workflow diagram module

bindAsService(context, TYPES.ISelectionListener, MySelectionListener);

This fails on master with a circular dependency error but works with this change.

Fixes eclipse-glsp/glsp/issues/1166

[martin-fleck-at]

LGTM!