Resilient stream example with connection retry

[bborutenko]

This change resolves issue #809
This revised example demonstrates a robust streaming consumer that does not panic on the first transient network error (e.g., BrokerTransportFailure on IPv6 ::1 for localhost). Instead, it restarts the stream with an exponential backoff, allowing librdkafka to retry and fall back to alternative broker addresses (such as 127.0.0.1) when available. The processing of messages remains asynchronous via tokio::spawn, while the outer loop handles stream errors gracefully and continuously attempts to reconnect.