Ensure NuSpecs for transport packages conform to NuGet guidance

[rladuca]

While creating #2138, we ran into NU5128 and NU5131.

According to NuGet guidance, we should be creating a reference group for all of our reference DLLs (see here).

This should fix both warnings.

NU5128

Some target frameworks declared in the dependencies group of the nuspec and the lib/ref folder do not have exact matches in the other location.

NU5131

References were found in the nuspec, but some reference assemblies were not found in both the nuspec and ref folder.