Consider alternatives to Moq

[philliphoff]

Recent events related to the Moq .NET test mock library have exposed potential privacy concerns. While versions of the library related to those concerns have been delisted from NuGet, to eliminate any exposure to those concerns in the future, alternatives should be considered (e.g. NSubstitute).

For example, here is a branch with the required to move to NSubstitute.

[jhurdlow]

I think the simpler thing would be for Microsoft to take a lead on this by forking Moq (call it FreeMoq or whatever) and move to that. Some random person doing that might not gain traction, but I believe people would happily all switch over if MS did it. We leave Moq in the dust and no one has to change their code. Just switch dependencies and be done.