Move LadspaWidgetFactory to LadspaEffect

Move the class `LadspaWidgetFactory` to the project LadspaEffect to make
it hopefully compile with mingw32 and mingw64.

Interestingly the code compiled and worked under Linux and MacOS.

include/LadspaWidgetFactory.h

@@ -1,49 +0,0 @@
-/*
- * LadspaWidgetFactory.h - Factory that creates widgets for LADSPA ports
- *
- * Copyright (c) 2023 Michael Gregorius
- *
- * This file is part of LMMS - https://lmms.io
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public
- * License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public
- * License along with this program (see COPYING); if not, write to the
- * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
- * Boston, MA 02110-1301 USA.
- *
- */
-
-#ifndef LMMS_GUI_LADSPA_WIDGET_FACTORY_H
-#define LMMS_GUI_LADSPA_WIDGET_FACTORY_H
-
-
-class QWidget;
-
-namespace lmms
-{
-
-class LadspaControl;
-
-namespace gui
-{
-
-class LadspaWidgetFactory
-{
-public:
-	static QWidget * createWidget(LadspaControl * ladspaControl, QWidget * parent);
-};
-
-} // namespace gui
-
-} // namespace lmms
-
-#endif // LMMS_GUI_LADSPA_WIDGET_FACTORY_H