Automatic migration from autoqueue to auto_merge_conditions

The queue_rules[].autoqueue field has been deprecated in favor of merge_protection_settings.auto_merge_conditions. Mergify now opens a migration PR that rewrites your configuration automatically. Mixed setups — where only some queues had autoqueue: true — are translated into the equivalent auto_merge_conditions, with a YAML comment marking the queues that remain manual-only and reachable via the /queue command.