Add missing parent for messagebox and other popups

Unparented popups can easily get lost in backround, but they still block top level event loop when run with ::exec() thus preventing interactions with main window.  This mainly happens on wayland. Setting the parent ensures they are always kept on top and reasonably positioned.

src/Mod/PartDesign/Gui/SketchWorkflow.cpp

@@ -651,7 +651,7 @@ private:
         Gui::TaskView::TaskDialog *dlg = Gui::Control().activeDialog();
         PartDesignGui::TaskDlgFeaturePick *pickDlg = qobject_cast<PartDesignGui::TaskDlgFeaturePick *>(dlg);
         if (dlg && !pickDlg) {
-            QMessageBox msgBox;
+            QMessageBox msgBox(Gui::getMainWindow());
             msgBox.setText(QObject::tr("A dialog is already open in the task panel"));
             msgBox.setInformativeText(QObject::tr("Do you want to close this dialog?"));
             msgBox.setStandardButtons(QMessageBox::Yes | QMessageBox::No);