Use IsTopNavigationDomain() in accelerator handling code in all ports

This is more correct than IsTopLevel() as accelerators shouldn't traverse the
"navigation domain" boundaries, by definition, and, even more importantly in
practice, some TLWs shouldn't stop the accelerators propagation, see the next
commit.

See #16870.

src/gtk/window.cpp

@@ -1105,7 +1105,7 @@ gtk_window_key_press_callback( GtkWidget *WXUNUSED(widget),
 
                 break;
             }
-            if (ancestor->IsTopLevel())
+            if (ancestor->IsTopNavigationDomain())
                 break;
             ancestor = ancestor->GetParent();
         }

src/msw/evtloop.cpp

@@ -137,7 +137,7 @@ bool wxGUIEventLoop::PreProcessMessage(WXMSG *msg)
         // stop at first top level window, i.e. don't try to process the key
         // strokes originating in a dialog using the accelerators of the parent
         // frame - this doesn't make much sense
-        if ( wnd->IsTopLevel() )
+        if ( wnd->IsTopNavigationDomain() )
             break;
     }
 
@@ -151,7 +151,7 @@ bool wxGUIEventLoop::PreProcessMessage(WXMSG *msg)
         // if we don't do this, pressing ESC on a modal dialog shown as child
         // of a modal dialog with wxID_CANCEL will cause the parent dialog to
         // be closed, for example
-        if ( wnd->IsTopLevel() )
+        if ( wnd->IsTopNavigationDomain() )
             break;
     }
 

src/osx/window_osx.cpp

@@ -2761,7 +2761,7 @@ bool wxWindowMac::OSXHandleKeyEvent( wxKeyEvent& event )
                 break;
             }
 
-            if (ancestor->IsTopLevel())
+            if (ancestor->IsTopNavigationDomain())
                 break;
 
             ancestor = ancestor->GetParent();