No Job Functions Found error should come from a different layer and with different description

The error message reported in https://github.com/Azure/azure-functions-dotnet-worker/issues/2029 is surfacing WebJobs concepts which are not relevant to Functions scenarios and may lead users down the wrong path for remediation. The host should be the one providing guidance to the user in this scenario.

Start with the linked Azure Functions .NET worker issue and trace where the “No Job Functions Found” error is currently surfaced in the host. The host should provide scenario-relevant guidance without exposing WebJobs concepts; done means the error comes from the host layer with a corrected description.

Written by the indexing model from the issue text.