hs: Circuitmap changes for prop224

This is part of the groundwork for service implementation of prop224 (legacy/trac#20657 (moved)).

First, we need the circuitmap API to use a circuit_t instead of or_circuit_t so we can use it on the service side which uses origin_circuit_t.

Second, add a service side API to track service circuits.

Finally, refactor this API so the naming has better semantic.