Fix image arrange.
Fix image arrange.

`Image` was calculating its desired size correctly according to the value of `Stretch` but then was not applying that calculation to the arrange pass.

Fixes #2260

AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,grokys/Perspex,wieslawsoltes/Perspex,SuperJMN/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,Perspex/Perspex,jkoritzinsky/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,SuperJMN/Avalonia,jkoritzinsky/Avalonia,Perspex/Perspex,SuperJMN/Avalonia,jkoritzinsky/Perspex,grokys/Perspex,akrisiun/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia