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/mrichtextedit.cpp

@@ -201,8 +201,7 @@ MRichTextEdit::MRichTextEdit(QWidget *parent, QString textIn) : QWidget(parent)
 
     // font size
 
-    QFontDatabase db;
-    const auto sizes = db.standardSizes();
+    const auto sizes = QFontDatabase::standardSizes();
     for(int size: sizes) {
         f_fontsize->addItem(QString::number(size));
     }
@@ -430,7 +429,11 @@ void MRichTextEdit::textStyle(int index) {
         }
     if (index == ParagraphMonospace) {
         fmt = cursor.charFormat();
+#if QT_VERSION < QT_VERSION_CHECK(5,13,0)
         fmt.setFontFamily(QString::fromUtf8("Monospace"));
+#else
+        fmt.setFontFamilies(QStringList() << QString::fromUtf8("Monospace"));
+#endif
         fmt.setFontStyleHint(QFont::Monospace);
         fmt.setFontFixedPitch(true);
         }