macOS: create application menu as QCocoaNSMenu with delegate

This way we can handle keyboard shortcuts for actions in that menu as
well in our menuHasKeyEquivalent implementation. This allows the focus
widget to accept the override, and e.g. a QKeySequenceEdit to record
Cmd+Q which with a plain NSMenu will just quit the application.

Pick-to: 6.3 6.2
Fixes: QTBUG-103590
Change-Id: I84597307aef8f0ab65d97d78e5aa15e5cf2e707d
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/plugins/platforms/cocoa/qcocoamenuloader.mm

@@ -56,7 +56,7 @@
         NSMenuItem *appItem = [[[NSMenuItem alloc] init] autorelease];
         appItem.title = appName;
         [theMenu addItem:appItem];
-        appMenu = [[NSMenu alloc] initWithTitle:appName];
+        appMenu = [[QCocoaNSMenu alloc] initWithoutPlatformMenu:appName];
         appItem.submenu = appMenu;
 
         // About Application

src/plugins/platforms/cocoa/qcocoansmenu.h

@@ -28,6 +28,7 @@ QT_DECLARE_NAMESPACED_OBJC_INTERFACE(QCocoaNSMenuDelegate, NSObject <NSMenuDeleg
 QT_DECLARE_NAMESPACED_OBJC_INTERFACE(QCocoaNSMenu, NSMenu
 @property (readonly, nonatomic) QCocoaMenu *platformMenu;
 - (instancetype)initWithPlatformMenu:(QCocoaMenu *)menu;
+- (instancetype)initWithoutPlatformMenu:(NSString *)menu;
 )
 
 QT_DECLARE_NAMESPACED_OBJC_INTERFACE(QCocoaNSMenuItem, NSMenuItem

src/plugins/platforms/cocoa/qcocoansmenu.mm

@@ -51,6 +51,13 @@ static NSString *qt_mac_removePrivateUnicode(NSString *string)
     return self;
 }
 
+- (instancetype)initWithoutPlatformMenu:(NSString *)title
+{
+    if (self = [super initWithTitle:title])
+        self.delegate = [QCocoaNSMenuDelegate sharedMenuDelegate];
+    return self;
+}
+
 - (QCocoaMenu *)platformMenu
 {
     return _platformMenu.data();