DolphinQt: Use non-autodismissable menus in menu bar.

A new class that derives from `QMenu` has been introduced. Menus of this
`NonAutodismissibleMenu` type will stay visible when a _checkable_
action is triggered.

This is convenient in menus that feature a series of check boxes that
toggle visibility of third components (e.g. the **List Columns** menu),
allowing the user to toggle several actions at once.

For now, the new type is used in the top menu bar.

Source/Core/DolphinQt/QtUtils/NonAutodismissibleMenu.cpp

@@ -0,0 +1,28 @@
+// Copyright 2025 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "DolphinQt/QtUtils/NonAutodismissibleMenu.h"
+
+#include <QAction>
+#include <QMouseEvent>
+
+namespace QtUtils
+{
+
+void NonAutodismissibleMenu::mouseReleaseEvent(QMouseEvent* const event)
+{
+  if (!event)
+    return;
+
+  QAction* const action{activeAction()};
+  if (action && action->isEnabled() && action->isCheckable())
+  {
+    action->trigger();
+    event->accept();
+    return;
+  }
+
+  QMenu::mouseReleaseEvent(event);
+}
+
+}  // namespace QtUtils