Message loss with receiveMessages in receiveAndDelete mode

When the maxWaitTime is smaller such as 1500ms, calling await receiver.receiveMessages(50, { maxWaitTimeInMs: 1500 }) repeatedly in a while loop causes message loss.

Reason could be the placement of drain call.

• Not seen with larger maxWaitTime.
• Not seen with subscribe (more reason to believe the issue is related to draining credits)
• Behavior is seen better with partitioned queues than unpartitioned (since receiving from partitioned queues is relatively slower when compared).

Code to repro - https://github.com/HarshaNalluru/sb-2048-issues/blob/main/message-loss-repro.ts

Observed while working on #14060