CppEditor: Convert parts of ModelManagerInterface to FilePath

Change-Id: If7503b6d6732e1735eb8d48ece6e80886d10c647
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/clangcodemodel/clangtextmark.cpp

@@ -43,7 +43,7 @@ namespace {
 
 Project *projectForCurrentEditor()
 {
-    const QString filePath = currentCppEditorDocumentFilePath();
+    const FilePath filePath = currentCppEditorDocumentFilePath();
     if (filePath.isEmpty())
         return nullptr;