ControllerInterface: Implement ChangeWindow on DInput without recreating the devices

Also polished DInput code in general to try and mitigate issue 11702.
Added a lot of logging and comments.

Source/Core/InputCommon/ControllerInterface/DInput/DInput.h

@@ -20,4 +20,6 @@ BOOL CALLBACK DIEnumDevicesCallback(LPCDIDEVICEINSTANCE lpddi, LPVOID pvRef);
 std::string GetDeviceName(const LPDIRECTINPUTDEVICE8 device);
 
 void PopulateDevices(HWND hwnd);
+void ChangeWindow(HWND hwnd);
+void DeInit();
 }  // namespace ciface::DInput