[Style] Warn about the broken Windows native styles and stop resolving System to them (#7461)

* [Style] Fall back to the built-in windows style instead of windowsvista

The Windows Vista native style is broken the same way as the Windows 11 one,
so the sanitizer now catches both and falls back to the built-in QWindowsStyle
instead of the Vista plugin. The style picker no longer offers either.

* [Style] Keep Windows native styles selectable but warn about them

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/interface/widgets/settings_page/appearance_settings_page.h

@@ -22,6 +22,7 @@ private slots:
     void openThemeLocation();
     void editPalette();
     void updateHomeTabSettingsVisibility();
+    void updateStyleWarning();
     void showShortcutsChanged(QT_STATE_CHANGED_T enabled);
     void overrideAllCardArtWithPersonalPreferenceToggled(QT_STATE_CHANGED_T enabled);
 
@@ -37,6 +38,7 @@ private:
     QComboBox schemeCombo;
     QLabel styleComboLabel;
     QComboBox styleCombo;
+    QLabel styleWarningLabel;
     QPushButton editPaletteButton;
 
     QLabel homeTabBackgroundSourceLabel;