ICore: Change some path API to use FilePath

Change-Id: Id841d6177206a021c9e606ce560b47d1ae6e52b9
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: hjk <hjk@qt.io>

src/libs/utils/fileutils.h

@@ -81,6 +81,7 @@ public:
     QString toString() const;
     QFileInfo toFileInfo() const;
     QVariant toVariant() const;
+    QDir toDir() const;
 
     QString toUserOutput() const;
     QString shortNativePath() const;