[storage/groups] return nodes DC and Hosts in VDisks data

[artemmufazalov]

Currently we have only NodeId, we use this NodeId to get data from viewer/nodelist handler. It will be much easier if everything will be present inside storage/groups VDisk (or PDisk) data.

We need data about node DC and Host, DC is needed to visually group vdisk in Storage table, Host is displayed inside popups.

[adameat]

after some thinking it was decided to keep current approach to get better performance and smaller responses.