[V1] OperationCanceledExceptions in user code causes Service Bus retry to not happen

When an OperationCanceledException occurrs in **pre-compiled C# functions** triggered by a Service Bus Topic, the function is not retried. When other exceptions (ex. System.Exception) are thrown, the function is retried.

```
//case that function is retried
throw new System.Exception("foo");

//case that function isn't retried
throw new System.Threading.TasksTaskCanceledException("bar");
```

Here is the [relevant retry code](https://github.com/Azure/azure-webjobs-sdk/blob/34036368a5b0ebcdecf9dd7fdd494ac6664d8c49/src/Microsoft.Azure.WebJobs.ServiceBus/MessageProcessor.cs#L67-L85).

Note that this does not repro in C# script functions (.csx). This is because there's a bug somewhere that special-case handles OperationCanceledexceptions, and C# function exceptions come back wrapped as a `FunctionInvocationException`.

## Workaround ##
Try-catch all business logic, and then re-throw any exceptions in a custom wrapper function.
```
[FunctionName("HandledServiceBusFunction")]
public static void Run([ServiceBusTrigger("mytopi", "subscription", AccessRights.Manage, Connection = "ServiceBus")]string mySbMsg, TraceWriter log)
{
log.Info($"ServiceBus topic trigger function processed message: {mySbMsg}");
try
{
ThrowMyException();
}
catch (Exception e)
{
throw new CustomException("This is my custom exception.", e);
}
}

private static void ThrowMyException()
{
// Can be any exception
throw new OperationCanceledException("Task canceled.");
}
```

**Note:** Unverified, but may be an issue with v2 as well.

Start with src/Microsoft.Azure.WebJobs.ServiceBus/MessageProcessor.cs at the linked retry logic and compare handling of OperationCanceledException with other exceptions. Reproduce the behavior in a pre-compiled C# Service Bus Topic function, contrasting it with the provided C# script case; done means cancellation exceptions trigger the same retry behavior without the workaround.

Written by the indexing model from the issue text.