Create a dotnet worker test repo and implement Host-Worker scenario tests

Create an internal repository to store .NET Worker specific tests migrated from the Host repo, and add new tests that validate Worker-side scenarios with the Host.

The issue names the Azure Functions Host repository but no files, existing tests, or entry points. Start by identifying the .NET Worker tests to migrate from the Host repository and the repository setup needed for them. Done means an internal test repository exists and includes the migrated tests plus new Host-Worker scenario coverage.

Written by the indexing model from the issue text.