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/TechDraw/Gui/Command.cpp

@@ -424,7 +424,7 @@ void CmdTechDrawView::activated(int iMsg)
             bool dontShowAgain = hGrp->GetBool("DontShowInsertFileMessage", false);
             if (!dontShowAgain) {
                 auto msgText = QObject::tr("If you want to insert a view from existing objects, please select them before invoking this tool. Without a selection, a file browser will open, to insert a SVG or image file.");
-                QMessageBox msgBox;
+                QMessageBox msgBox(Gui::getMainWindow());
                 msgBox.setText(msgText);
                 auto dontShowMsg = QObject::tr("Do not show this message again");
                 QCheckBox dontShowCheckBox(dontShowMsg, &msgBox);

src/Mod/TechDraw/Gui/CommandExtensionDims.cpp

@@ -113,7 +113,7 @@ void execInsertPrefixChar(Gui::Command* cmd, std::string prefixFormat, const QAc
 
     std::string prefixText(prefixFormat);
     if (prefixFormat.find("%s") != std::string::npos) {
-        DlgTemplateField ui;
+        DlgTemplateField ui(Gui::getMainWindow());
         const int MAX_PREFIX_LENGTH = 31;
 
         if (action) {

src/Mod/TechDraw/Gui/TemplateTextField.cpp

@@ -30,6 +30,7 @@
 #endif // #ifndef _PreCmp_
 
 #include <Base/Console.h>
+#include <Gui/MainWindow.h>
 
 #include <Mod/TechDraw/App/DrawTemplate.h>
 #include <Mod/TechDraw/App/DrawSVGTemplate.h>
@@ -73,7 +74,7 @@ void TemplateTextField::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
     if ( tmplte && m_rect->rect().contains(event->pos()) ) {
         event->accept();
 
-        DlgTemplateField ui;
+        DlgTemplateField ui(Gui::getMainWindow());
 
         ui.setFieldName(fieldNameStr);
         ui.setFieldContent(tmplte->EditableTexts[fieldNameStr]);