New `azure_event_hubs` sink

Azure Event Hubs is like a managed Kafka service:

Allow existing Apache Kafka clients and applications to talk to Event Hubs without any code changes—you get a managed Kafka experience without having to manage your own clusters.

This suggests that we could wrap the existing kafka sink. I'd prefer that we wrap it since it is technically a different service. We also get the marketing benefit (guides, ets) when we create a new sink.