[EventHubs] Get IoT Hub Name from Redirect Address in sample (Azure#19314)

Fixes: Azure#19087 
Follows[ C# sample,](https://github.com/Azure/azure-sdk-for-net/blob/350c23ea19ed76d74f7d97dfe3aec82671fdcc9d/samples/iothub-connect-to-eventhubs/IotHubConnection.cs#L97) which also gets IoT Hub name from redirect address.

Author: swathipil

sdk/eventhub/azure-eventhub/samples/async_samples/iot_hub_connection_string_receive_async.py

@@ -15,6 +15,7 @@
 """
 
 import os
+import re
 import time
 from base64 import b64encode, b64decode
 from hashlib import sha256
@@ -80,6 +81,13 @@ def convert_iothub_to_eventhub_conn_str(iothub_conn_str):
         # Once a redirect error is received, close the original client and recreate a new one to the re-directed address
         receive_client.close()
         fully_qualified_name = redirect.hostname.decode("utf-8")
+        # Use regular expression to parse the Event Hub name from the IoT Hub redirection address
+        if redirect.address:
+            # The regex searches for the Event Hub compatible name in the redirection address. The name is nested in
+            # between the port and 'ConsumerGroups'.
+            # (ex. "...servicebus.windows.net:12345/<Event Hub name>/ConsumerGroups/...").
+            # The regex matches string ':<digits>/', then any characters, then the string '/ConsumerGroups'.
+            iot_hub_name = re.search(":\d+\/.*/ConsumerGroups", str(redirect.address)).group(0).split("/")[1]
         return "Endpoint=sb://{}/;SharedAccessKeyName={};SharedAccessKey={};EntityPath={}".format(
             fully_qualified_name,
             shared_access_key_name,