Memory utilization and service bus exceptions improvement

Notification service creates a lot of threads when number of partitions and number of registrations increase. We observed high memory usage and a lot of service bus connection exceptions in our production environments due to this. To tackle this, we decreased thread stack size with java options on the container. We also increased the messageWaitDuration for service bus subscription handler (default value is 60s. It is currently set to 1s, which is very aggressive). This change is to address a lot of timeout exceptions we observed on service bus