Make AutoSubscribe throw when missing publisher route

[timbussmann]

With 7.1 and 6.5 the AutoSubscribe behavior was changed to log an error when a event type cannot be subscribed to (due to a missing RegisterPublisher configuration). This only affects transports using message driven pub/sub.

There were goals to make AutoSubscribe throw an exception instead of logging an error, similar to how Subscribe also throws an exception when subscribing manually to an event type with a missing publisher address. This idea was discarded in order to not introduce breaking behavior in a minor version. This idea should be revisited on the next major version to help users to avoid missing publisher configurations (and therefore missing events).

[SeanFeldman]

This only affects transports using message driven pub/sub.

It also affects the transports with native pub/sub. Azure Service Bus is affected as well. Particular/NServiceBus.Transport.AzureServiceBus#55