Change: [Script] Move GSStation::GetOwner to GSBaseStation::GetOwner (#13406)

* Add: [Script] GSBaseStation::GetOwner

Added method for Game Scripts to retrieve the owner of a basestation.

* Cleanup: [Script] Remove ScriptStation::GetOwner

Due to class inheritance, GSStation::GetOwner and GSWaypoint::GetOwner can both reach GetOwner defined at GSBaseStation.

src/script/api/game_changelog.hpp

@@ -28,6 +28,7 @@
  * \li GSCargo::CC_POTABLE
  * \li GSCargo::CC_NON_POTABLE
  * \li GSVehicleList_Waypoint
+ * \li GSBaseStation::GetOwner
  *
  * Other changes:
  * \li GSBridge::GetBridgeID renamed to GSBridge::GetBridgeType