Add automatic correlation/dependency tracking for Azure EventHubs messages

[stijnmoreels]

Is your feature request related to a problem? Please describe.
We have provided an easy way to send correlated Azure Service Bus messages with dependency tracking, but we don't have something like this for Azure EventHubs.

Describe the solution you'd like
Create a set of extensions on the EventHubProducerClient that provides similar functionality as with the Azure Service Bus variant. We should also make sure that we have an EventDataBuilder to create such a correlated event message so people can decide how to use correlation.