Adapt QQuickWindow::createTextureFromNativeObject() to new platform abstraction pattern

In other platform-specific API we are moving away from casts between void* etc. from platform handles, and we could aim for the same approach in createTextureForNativeObject (and maybe other places).

It could look something like this:

class QSGOpenGLTexture 
{
public:
    static QSGTexture *createTexture(QQuickWindow *window, GLuint id, const QSize &size); 
};

And similar factory functions for other backends. That way we get rid of the quint64 cast in QQuickWindow and make the function type-safe, plus it will be more consistent with QPA APIs in Qt 6.