stackLiftEnabled property Null safety
Tell if stack lift is enabled. This is considered part of the controller's state, but note that the status from a running program reflects back to when a program isn't running. This is important for proper functioning of the R/S key, and SST. The value comes from the RealController.
@protected bool get stackLiftEnabled => controller._stackLiftEnabled;
@protected set stackLiftEnabled(bool v) => controller._stackLiftEnabled = v;