CassandraSinkCluster fix connecting to non-local clusters

[rukai]

closes #767

The problem was caused by TcpStream::connect blocking indefinitely when given a meaningless local ip instead of the global ip that we actually meant to give it.
The fix is: when generating the node list we need to query the correct system.local field broadcast_address that gives us the global ip that we actually wanted, instead of listen_address which gives us the local ip.

[github-actions]

1 benchmark regressed. 0 benchmark improved. Please check the benchmark workflow logs for full details: https://github.com/shotover/shotover-proxy/actions/runs/2953148101

  1 (1.00%) low mild
  5 (5.00%) high mild
  1 (1.00%) high severe
transform/cassandra_request_throttling_unparsed
                        time:   [1.0342 us 1.0408 us 1.0482 us]
                        change: [+22.825% +25.479% +27.819%] (p = 0.00 < 0.05)
                        Performance has regressed.