Domain types and capability traits for jip.
Users of this crate get a coherent view of a Linux host's network: L1 kernel
primitives (Link, Addr, Route, Neighbor, Socket), L2 domain concepts
(Connection, Service, Path, Flow), L3 judgments (Finding, Health),
and L4 capability traits that backends implement.
There is no I/O in this crate. Backends live in sibling crates.