fix(gtk): Fix get scan code in GtkKeyboardInputSource

See https://docs.gtk.org/gdk3/method.Event.get_scancode.html

Reference unoplatform#16670

src/Uno.UI.Runtime.Skia.Gtk/Input/GtkKeyboardInputSource.cs

@@ -49,15 +49,15 @@ private void OnKeyPressEvent(EventKey evt)
 				this.Log().Trace($"OnKeyPressEvent: {evt.Key} -> {virtualKey}");
 			}
 
-			InputHelper.TryConvertKeyCodeToScanCode(evt.HardwareKeycode, out var scanCode);
+			var scanCode = EventHelper.GetScancode(evt);
 
 			KeyDown?.Invoke(this, new(
 					"keyboard",
 					virtualKey,
 					GetKeyModifiers(evt.State),
 					new CorePhysicalKeyStatus
 					{
-						ScanCode = scanCode,
+						ScanCode = (uint)scanCode,
 						RepeatCount = 1,
 					},
 					KeyCodeToUnicode(evt.HardwareKeycode, evt.KeyValue)));
@@ -79,15 +79,15 @@ private void OnKeyReleaseEvent(EventKey evt)
 				this.Log().Trace($"OnKeyReleaseEvent: {evt.Key} -> {virtualKey}");
 			}
 
-			InputHelper.TryConvertKeyCodeToScanCode(evt.HardwareKeycode, out var scanCode);
+			var scanCode = EventHelper.GetScancode(evt);
 
 			KeyUp?.Invoke(this, new(
 					"keyboard",
 					virtualKey,
 					GetKeyModifiers(evt.State),
 					new CorePhysicalKeyStatus
 					{
-						ScanCode = scanCode,
+						ScanCode = (uint)scanCode,
 						RepeatCount = 1,
 					},
 					KeyCodeToUnicode(evt.HardwareKeycode, evt.KeyValue)));