more efficient dependency conditions

[alexhsamuel]

To support large numbers of active dependencies, don't poll for conditions.

1. Add a mechanism to block until a run transitions, for a certain subset of runs. For the existing set of condition types, limiting this to runs of a single job ID is sufficient. We can mostly re-use the existing RunStore.query_live queuing mechanism, with the addition of further filters.
2. Split the Condition base into two subtypes: RunCondition and PolledCondition. The former will use query_live.

with run_store.query_live(job_id=job_id, args=args, state=state) as queue:
    run = await queue.get()
    log.info(f"dependency satisfied: {run}")