The contract between the model and platform backends.
net-lattice-platform depends only on net-lattice-core — never on
net-lattice-model. Its provider traits describe the shape of a
contract, not the content of the model, via associated types. See
ARCHITECTURE.md for the full rationale, including how model
convergence is enforced one layer up, in lattice.
Stage 0.4 added InterfaceProvider; Stage 0.5 added DnsProvider;
Stage 0.6 added NeighborProvider; Stage 0.7 added AddressProvider;
Stage 0.8 adds EventProvider.