[world] Support for `SurrealDB`

[sepcnt]

Hello, I'm working on a SurrealDB adapter for vercel/workflow — building a durable workflow engine and broker backed by SurrealDB.
Most of the listen/notify logic from Graphile can be migrated to SurrealDB's LIVE queries. After extensive experimentation, SurrealDB with a memory backend achieves roughly 0.7× the performance of PostgreSQL.
The remaining ~30% gap comes down to two factors: per-message WebSocket JSON overhead, and SurrealDB's optimistic concurrency model. Additionally, LIVE SELECT is inherently noisy — every lane mutation notifies all workers. This is a necessary cost of the current architecture, since edge-triggered signaling would starve workers.