Test updates

[bording]

Proposed Changes

This includes a few changes needed to clean up some cruft in the test project and allow for the testing packages to be updated, including Microsoft.NET.Test.Sdk as mentioned in #673.

From what I can tell, the main reason that Microsoft.NET.Test.Sdk 16.4.0 was causing no tests to be found was that it moved to supporting netcoreapp2.1 because netcoreapp2.0 is no longer supported.

After making that change, I was able to update to 16.4.0 and the tests were being discovered and run properly when using the test scripts, but I noticed that the tests were not working when run from Visual Studio. It looks like 16.3.0 introduced a bug which 16.4.0 also has. I had to move down to 16.2.0 to avoid the bug. This has the tests working in VS, and both test scripts.

I'm going to be filing a bug against the Test SDK repo to hopefully get that fixed.

I also added the new reference assembly package, which should let the main project be fully built on linux, which should help with removing mono as a dependency to build and pack this project.

NOTE: I tested all of this on the .NET Core 3.1.100 SDK, and I advise updating your build agents to the latest version as well.

Types of Changes

What types of changes does your code introduce to this project?
Put an x in the boxes that apply

• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating
the PR. If you're unsure about any of them, don't hesitate to ask on the
mailing list. We're here to help! This is simply a reminder of what we are
going to look for before merging your code.

• I have read the CONTRIBUTING.md document
• I have signed the CA (see https://cla.pivotal.io/sign/rabbitmq)
• All tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in related repositories

[michaelklishin]

Thank you, works as advertised 👍

[lukebakken]

@bording do you think that backporting this change to the 5.x branch to be included in the 5.2.0 release is appropriate? I'm pretty sure it is but I would like your expertise.

I'll probably be pinging you about other changes to master since version 5.1.2. I'm reviewing them all for backporting to 5.x.

[bording]

Yes, it should be fine to backport these changes.