Scopes and batch lineage in queue event logs

The action.queue.checks_start, action.queue.checks_end, and action.queue.leave events now include the batch’s scopes and its parent_batch_ids.

scopes tell you which parallel lane a batch ran in: batches with disjoint scopes check concurrently. parent_batch_ids let you chain a batch back to the ones it inherited check results from. action.queue.leave also gains a batch_id, the batch the pull request was in when it left, so you can correlate a leave with its checks.

Together these let you rebuild what the queue was checking at a point in time from the event logs alone.

We also renamed train_car_id to batch_id on the check and bisection events. train_car_id still ships as a deprecated alias with the same value, so existing integrations keep working.