Add MSTest among suggested new workloads when calling dotnet new

[nohwnd]

Summary

add mstest template among the common templates suggested by dotnet new

https://grep.app/search?q=Common%20templates%20are%3A

Background and Motivation

Make our test framework more visible.

Proposed Feature

Add mstest among the suggested common templates.

Alternative Designs

[Evangelink]

I would love to! Let's make sure we do a meeting with some key folks to ensure this is not going to trigger any kind of complaints from users (or that we are ok with it).