Add extra properties to relays/vertices from their descriptors

From https://gitlab.torproject.org/tpo/team/-/wikis/GSoC#1-relay-to-relay-connectivity-in-the-tor-network

This can be further improved in several ways, for instance by adding properties to the vertices like country, ASN, flags, family, etc. This would allow it to analyze separately the cyclic non-exits subgraphs and the acyclic exits subgraphs. It'd also be possible to detect whether some subgraphs are not connected because of families, ASN or other reasons.