Pass node features through to RouteHops

Pass node features through to RouteHops

This exposes the latest Init-context features in the ChannelDetails
passed to the Router during route calculation, which combines those
with the Node-context features tracked from node_announcements to
provide the latest Node-context features in RouteHop structs.

Fields are also added for Channel-context features, though those are
only partially used since no such features are defined today anyway.

These will be useful when determining whether to use new
TLV-formatted onion hop datas when generating onions for peers.