Treat the accessible non-editable combobox as ButtonMenu on macOS

Following the system design, we should treat the non-editable combobox
as a ButtonMenu. All of the similar elements in macOS's UI are called
ButtonMenu with the screen reader.

This fixes the case when ctrl+option+space does not invoke the popup
menu with options.

Fixes: QTBUG-106162
Change-Id: I0b439c56d72d1fe5b32a60eb7c001f863c00adc1
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/plugins/platforms/cocoa/qcocoaaccessibility.mm

@@ -155,6 +155,8 @@ NSString *macRole(QAccessibleInterface *interface)
 
     if (roleMap.contains(qtRole)) {
        // MAC_ACCESSIBILTY_DEBUG() << "return" <<  roleMap[qtRole];
+        if (roleMap[qtRole] == NSAccessibilityComboBoxRole && !interface->state().editable)
+            return NSAccessibilityMenuButtonRole;
         if (roleMap[qtRole] == NSAccessibilityTextFieldRole && interface->state().multiLine)
             return NSAccessibilityTextAreaRole;
         return roleMap[qtRole];

src/widgets/accessible/complexwidgets.cpp

@@ -366,6 +366,7 @@ QAccessible::State QAccessibleComboBox::state() const
 
     s.expandable = true;
     s.expanded = isValid() && comboBox()->view()->isVisible();
+    s.editable = comboBox()->isEditable();
 
     return s;
 }