C# Templates should have Microsoft.VisualStudio.Threading.Analyzers Added by Default

[FinVamp1]

As discussed with @paulbatum .

We have guidance around Async as discussed here.

https://docs.microsoft.com/en-us/azure/azure-functions/functions-best-practices#use-async-code-but-avoid-blocking-calls

By adding this analyzer to the template we have guidance on when the customer is not using Async properly for C#.

[kulkarnisonia16]

https://www.nuget.org/packages/Microsoft.VisualStudio.Threading.Analyzers/

[dariagrigoriu]

@FinVamp1 is following up on this item.