Microsoft.TemplateEngine.Authoring.Tasks is missing integration tests

[ViktorHofer]

This package recently got broken and will be fixed with https://github.com/dotnet/templating/pull/8952/. This highlighted that there aren't any integration tests running for that package. As this is an msbuild tasks package and targets .NET Framework and .NET, it should be validated that the package works with both desktop msbuild and core msbuild.