Implement `NetworkInfo` calls on full stack of Netmap services. Current
epoch is read from node local state, magic number is read via `MagicNumber`
call of morph client.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
Replace static NodeInfo structure with NodeState interface that provides
method to read node information in runtime.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>