Better helpers for working with a router's static routes

Better helpers for working with a router's static routes: a task in MiMo-V2.6-RL-oss: Agentic RL Environments (MiMo RL release). The libovsdb ops layer that wraps the OVN northbound database has helpers for logical router static routes, but two common needs are awkward to satisfy today: 1. Looking…