"No job functions found" after updating to 2.0.12050.0

I'm breaking out an issue from our announcements page into it's own topic for more back-and-forth. Original discussion started here: https://github.com/Azure/app-service-announcements-discussions/issues/64#issuecomment-417731957

From @jmsalvo

> I thought I made all the necessary updates following the 'breaking changes notice' details, but I am seeing this error "No job functions found. Try making your job classes and methods public. If you're using binding extensions (e.g. ServiceBus, Timers, etc.) make sure you've called the registration method for the extension(s) in your startup code (e.g. config.UseServiceBus(), config.UseTimers(), etc.). Then, I see "the binding types are not registered. Please ensure the type is correct and the binding extension is installed". As far as I am aware, I have all the extensions installed. Not sure what is meant by 'startup code', I presume I'm missing some configuration or setup that is now required in my function?
>
> I'm running locally in VisualStudio, I see a 'Starting Host' message indicating the Functions Runtime Version is 2.0.12050.0. The binding types the message suggests are not registered are: activityTrigger, eventGridTrigger and orchestrationTrigger.
>
> The following are the referenced packages:
> "Microsoft.Azure.WebJobs.Extensions.CosmosDB" Version="3.0.1-beta2"
> "Microsoft.Azure.WebJobs.Extensions.DurableTask" Version="1.6.0"
> "Microsoft.Azure.WebJobs.Extensions.EventGrid" Version="2.0.0-beta4"
> "Microsoft.Azure.WebJobs.Script.ExtensionsMetadataGenerator" Version="1.0.0"
> "Microsoft.NET.Sdk.Functions" Version="1.0.19"