Identify architecture of found MSBuild

[twsouthwick]

Can the VisualStudioInstance include information about what the architecture is? This is especially problematic as dotnet --list-sdks will list sdks for both x86 and x64 and will then fail to load some of the assemblies.

I'm not sure if we should use an existing type (ie System.Runtime.InteropServices.Architecture) or create something here, but it would be nice to just check there instead of my current check of if it contains 'x86' that can be problematic. The .version file contains the os-arch pair that can probably be used for this.