RETRY_REMOTE_DC

Enables the driver's native cross-DC failover (GH #58) — requires LoadBalancingConfig.dcAwareFailover = true and a non-empty LoadBalancingConfig.allowedRemoteDcs. The driver includes nodes from every DC in LoadBalancingConfig.allowedRemoteDcs in its query plans once local-DC nodes are exhausted; there is no ordering/priority across multiple allowed DCs.