Core: Fix compilation issues with Qt 6

- qrand() is gone
- adapt to incompatible change to QVariant constructor with custom types
- QAbstractItemView::viewOptions() is gone

Change-Id: I931d963fc4370077d628740ed90ca36c4e9ba1d5
Reviewed-by: hjk <hjk@qt.io>

src/plugins/coreplugin/dialogs/externaltoolconfig.cpp

@@ -49,6 +49,7 @@
 #include <QMenu>
 #include <QMimeData>
 #include <QPlainTextEdit>
+#include <QRandomGenerator>
 #include <QTextStream>
 
 using namespace Utils;
@@ -644,7 +645,7 @@ static QString getUserFilePath(const QString &proposalFileName)
         if (++count > 15)
             return QString();
         // add random number
-        const int number = qrand() % 1000;
+        const int number = QRandomGenerator().generate() % 1000;
         tryPath = newFilePath + QString::number(number) + suffix;
     }
     return tryPath;