Version.txt in model .zip should use the FileVersion, not AssemblyVersion #3132

When you save a model, it generates a Version.txt file in the .zip, so we can tell which version of ML.NET was used to generate the model.

However, the issue is we are using the AssemblyVersion there, which isn't great information as all the models produced are showing:

1.0.0.0

We should write the FileVersion or AssemblyInformationalVersion instead, which will give us the exact build and SHA:

[assembly: AssemblyFileVersion("0.12.27526.3")]
[assembly: AssemblyInformationalVersion("0.12.27526.3 @BuiltBy: dlab14-DDVSOWINAGE101 @Branch: master @SrcCode: https://github.com/dotnet/machinelearning/tree/9caafb04d2b4f298f2a9479a9550597afee32c94+9caafb04d2b4f298f2a9479a9550597afee32c94")]