Harvesting - improvements using statistics service - query node by nodePublicKey

[cryptoBeliever]

Blocking issue: symbol/statistics-service#95

Using statistics service we can improve the harvesting view:

• query node on which user started harvesting directly from statistics service instead of saving in local storage. For that in state service will be prepared option to query node by nodePublicKey (Add endpoint that will allow get node by nodePublicKey statistics-service#95). It will be possible to directly use the key from the node key link to check if an account is harvesting currently on that node.

• list of nodes can be also fetched from statistics service instead /node/peers. This probably requires pagination (Support pagination on node list. statistics-service#74) so we can split into separate task if needed.