Qt: Show dialog on startup for settings version mismatch

For the QMessageBox to appear, error reporting is performed again after
main window creation.

src/duckstation-qt/main.cpp

@@ -55,6 +55,8 @@ int main(int argc, char* argv[])
     window->startupUpdateCheck();
   }
 
+  window->reportSettingsVersionMismatchString();
+
   int result = app.exec();
 
   window.reset();

src/duckstation-qt/mainwindow.cpp

@@ -1088,6 +1088,13 @@ void MainWindow::startupUpdateCheck()
   checkForUpdates(false);
 }
 
+void MainWindow::reportSettingsVersionMismatchString()
+{
+  const QString mismatch_str = QString::fromStdString(m_host_interface->GetSettingsVersionMismatchString());
+  if (!mismatch_str.isEmpty())
+    reportError(mismatch_str);
+}
+
 void MainWindow::updateDebugMenuVisibility()
 {
   const bool visible = m_host_interface->GetBoolSettingValue("Main", "ShowDebugMenu", false);

src/duckstation-qt/mainwindow.h

@@ -30,6 +30,10 @@ public:
   /// Performs update check if enabled in settings.
   void startupUpdateCheck();
 
+  /// Reports m_host_interface's settings version mismatch string. Does nothing if string is empty (no settings version
+  /// mismatch detected).
+  void reportSettingsVersionMismatchString();
+
 public Q_SLOTS:
   /// Updates debug menu visibility (hides if disabled).
   void updateDebugMenuVisibility();