Feature - Run tests from many assemblies

[benguenter]

When there are multiple assemblies of tests for an FSharp project, it is a pain to run each project of tests individually using the dotnet cli. I think it's valuable to use the dotnet watch tooling as well which doesn't work as nicely with multiple test projects either. This PR adds the ability to specify multiple assemblies from the test runner in the Main.fs file when calling runTestsInAssembly. That way all the results show up in one big list and we can use useful tooling like dotnet watch on a single project.

[haf]

Is this ready to merge?

[benguenter]

Is this ready to merge?

Sure is!