v4.27.3: Improves background queue reliability and efficiency

Refactors the background queue to enhance reliability and efficiency by:

- Adding connection checks and reconnection logic to prevent job loss due to database connection issues.
- Implementing bulk processing for database operations to reduce the number of queries.
- Removing transaction management from the queue itself to rely on the application's transaction boundaries.
- Adding a dedicated connection for the consumer to allow updating job status even during application transaction rollbacks.
- Adding ext-pdo dependency.