Remove NATIVE from WINDOW statement

[danchanka]

Currently, the WINDOW statement includes an option NATIVE. In most contexts, NATIVE means that the object has already been created and only needs to be declared in the code so that the IDE can recognize and interact with it. However, in this context, NATIVE windows instantiate an object of the AbstractWindow class, while windows without the NATIVE option instantiate an object of the NavigatorWindow class. The NavigatorWindow class inherits from AbstractWindow and adds some additional functionality.

I propose refactoring the window creation process to eliminate the NATIVE option and consolidate the AbstractWindow and NavigatorWindow classes into a single, unified class.