Refactored platform options

[kekekeks]

#2365

Before:

public static AppBuilder BuildAvaloniaApp()
{
    var builder = AppBuilder.Configure<App>();
    if(RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
         builder.UseX11(new X11PlatformOptions() {UseGpu = false});
    else if(RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
         builder.UseAvaloniaNative(anopts => 
         {
              anopts.UseGpu = false;
              anopts.MacOptions.ShowInDock = 0;
         });
    else if(RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
          builder.UseWin32(false, true);
    return builder;
}

After:

public static AppBuilder BuildAvaloniaApp() => AppBuilder.Configure<App>()
     .UsePlatformDetect()
     .With(new X11PlatformOptions { UseGpu = false })
     .With(new AvaloniaNativePlatformOptions { UseGpu = false })
     .With(new MacOSPlatformOptions { ShowInDock = false })
     .With(new Win32PlatformOptions { UseDeferredRendering = false });

[grokys]

@kekekeks what you say "Not Tested", what in particular hasn't been tested, i.e. what should I be testing?

[kekekeks]

I haven't actually run the code on OSX/Windows.

[grokys]

LGTM, a big improvement 👍