Azure Event Provider can consume large amounts of threads in certain scenarios

Description

If code tries to send a large number of events through the Azure Event provider over a short time period, a large number of parallel threads are created. This might trigger throttling in Azure Service Bus, causing even more parallel threads to be created to handle new incoming events while previous events are being retried.

The Azure Event provider is supposed to limit the number of threads, and queue incoming events while existing events are being processed. The logic was not working as expected. It is now fixed.