Adds a `nextState` argument to access the future url from `CanDeactivate`. BEFORE: canDeactivate(component: T, route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<boolean>|Promise<boolean>|boolean; AFTER: canDeactivate(component: T, currentRoute: ActivatedRouteSnapshot, currentState: RouterStateSnapshot, nextState?: RouterStateSnapshot): Observable<boolean>|Promise<boolean>|boolean; Closes #9853