NoGUI/SDL: Save and restore window geometry

src/duckstation-nogui/sdl_host_interface.h

@@ -32,6 +32,9 @@ protected:
 private:
   void HandleSDLEvent(const SDL_Event* event);
 
+  void GetSavedWindowGeometry(int* x, int* y, int* width, int* height);
+  void SaveWindowGeometry();
+
   SDL_Window* m_window = nullptr;
   bool m_fullscreen = false;
   bool m_was_paused_by_focus_loss = false;