feat(monitoring): add lock_waits metric and dashboard

Dementii Priadkorequested to merge
feat/lock-waits-metric-and-dashboard into main

Add lock_waits metric to pgwatch-prometheus that provides detailed information about lock waits, including waiting and blocking processes with their queries, users, application names, and wait durations.

  • Add lock_waits metric with PostgreSQL 14+ support using query_id
  • Create Grafana dashboard with panels for lock wait counts, durations, lock types, and detailed lock wait information table

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