Migrate usage of deprecated ServiceBus packages

Our tests use a deprecated service bus package:

https://github.com/Azure/azure-functions-host/blob/1bf081347aa0ff3fa02e846802ae330611d192ff/test/WebJobs.Script.Tests.Integration/WebJobs.Script.Tests.Integration.csproj#L49

However, it also appears that the actual .cs files which use that are excluded from compile:

https://github.com/Azure/azure-functions-host/blob/1bf081347aa0ff3fa02e846802ae330611d192ff/test/WebJobs.Script.Tests.Integration/WebJobs.Script.Tests.Integration.csproj#L24-L28

We should either migrate this package, fix the tests, and include them. Or remove the package and test files altogether.

Start with the linked test/WebJobs.Script.Tests.Integration/WebJobs.Script.Tests.Integration.csproj, checking the deprecated ServiceBus package reference and the exclusions around lines 24–28. Locate the excluded C# test files, then determine whether migrating the package and enabling the tests or removing both package and tests is appropriate; done means the project builds without the deprecated package and the intended tests are handled.

Written by the indexing model from the issue text.