Dead key doesn't trigger KeyDown on macOS

[MrJul]

Describe the bug
The KeyDown event isn't raised for dead key presses in macOS, but the KeyUp event is.

To Reproduce
Press then release a dead key, for example ^ on an AZERTY keyboard.

Expected behavior
Both KeyDown and KeyUp events are raised.

Additional context
macOS Ventura

The dead key press results in setMarkedText being called, marking the key as handled, preventing the event for being triggered: https://github.com/AvaloniaUI/Avalonia/blob/655f199647c36b16cad24d68b14f38380c70c8ed/native/Avalonia.Native/src/OSX/AvnView.mm#L602C5-L602C21 (introduced by #11021)

[Gillibald]

I think we can add an additional check for that flag. We only need to set if if marked text actually has any content and content has changed

[MrJul]

Fixed by #12560