[Event Hubs] Ensure receiver is functional

[ramya-rao-a]

As per the API proposal in #2718 (comment), we will now have a createReceiver() method on the Event Hub Client that returns a receiver. A skeleton is already in place for the receiver. This issue is to ensure

• receiveBatch method works as expected
• getEventIterator method works as expected. (See https://github.com/ramya-rao-a/azure-sdk-for-js/blob/bd6e728d6d596022b98e5ed15d705721d13db004/sdk/eventhub/event-hubs/review/track2Sample.js#L42 for usage sample)
• receive method works as expected
• All tests in receiver.spec.ts are updated and pass
• receiver.close() should close all the underlying AMQP links. Further operations should throw error

Please note that this issue only ensures that the receive operations on the receiver works. We need to ensure #3176 is taken care of to call this feature of "createReceiver" actually complete

[ramya-rao-a]

Done with #3356