[node-split] Prepare node-service in similar way how smeshing-service is extracted from node.go

[jellonek]

Followup to #6625

The real code for node service should be extracted from node.go to node_service.go in the way how smeshing_service.go was done.

In effect we should keep current shape of service initialization/startup in node.go for legacy mode (for the transition time, but probably under different set of names) and create stripped down initialization/startup for node-service mode, by removing parts which should be available only on smeshing-service from a fresh copy of initServices/startServices.