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/osx/window_osx.cpp

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