pg_flight_recorder: Continuously sample PostgreSQL system state via pg_cron

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The pg_flight_recorder tool provides a continuous, low-overhead way to monitor PostgreSQL database health and performance by capturing detailed system state data. This enables quicker diagnosis and resolution of issues, improving reliability and uptime for database administrators and users alike.

• Continuous, background sampling of PostgreSQL metrics without external agents.
• Captures comprehensive data including wait events, locks, WAL activity, and query performance.
• Supports long-term analysis and anomaly detection with optional extensions.