TD: port to Qt6

* in QtConcurrent::run the order of 1st and 2nd argument are swapped
* QtConcurrent::run asserts that the argument of the passed function pointer is not non-const
* Used methods of QFontDatabase are static in Qt5 and Qt6
* QTextStream::setCodec() has been removed in Qt6
* Argument of enterEvent() has changed from QEvent to QEnterEvent
* QTextCharFormat::setFamily() is deprecated

src/Mod/TechDraw/Gui/QGSPage.cpp

@@ -1259,7 +1259,9 @@ void QGSPage::postProcessXml(QTemporaryFile& temporaryFile, QString fileName, QS
 
     QTextStream stream(&outFile);
     stream.setGenerateByteOrderMark(false);
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
     stream.setCodec("UTF-8");
+#endif
 
     stream << exportDoc.toByteArray();
     outFile.close();