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