Make Popup.IsOpen a direct property.
Make Popup.IsOpen a direct property.

This fixes Menu and DropDown.

wieslawsoltes/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,Perspex/Perspex,grokys/Perspex,akrisiun/Perspex,AvaloniaUI/Avalonia,OronDF343/Avalonia,jkoritzinsky/Avalonia,Perspex/Perspex,susloparovdenis/Avalonia,jkoritzinsky/Perspex,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,OronDF343/Avalonia,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,grokys/Perspex,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,AvaloniaUI/Avalonia,susloparovdenis/Perspex,MrDaedra/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,MrDaedra/Avalonia,susloparovdenis/Perspex,AvaloniaUI/Avalonia,punker76/Perspex,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,jazzay/Perspex,susloparovdenis/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia