Previously, DataNodeInfo.Id was used as the node address, which worked
when Id was always ip:port. Now that Id can be an explicit string,
we need a separate Address field for connection purposes.
Changes:
- Add 'address' field to DataNodeInfo protobuf message
- Update ToDataNodeInfo() to populate the address field
- Update NewServerAddressFromDataNode() to use Address (with Id fallback)
- Fix LookupEcVolume to use dn.Url() instead of dn.Id()
Ref: https://github.com/seaweedfs/seaweedfs/issues/7487