New API endpoint GET /v1/repos/{owner}/{repository}/stats/queues_checks_outcome_count that returns dequeue reason counts grouped by time intervals.
The existing merge_queue_checks_outcome endpoint only returns aggregate totals (useful for pie charts). This new endpoint enables time-series graphs showing how dequeue reasons (e.g. CHECKS_FAILED, MERGE_QUEUE_RESET, SUCCESS) evolve over time. The old endpoint is now deprecated.
Supports filtering by base branch, partition, queue name, and priority rule.