Migrate the Tails infra monitoring to Prometheus

Reference: TPA-RFC-73: Tails infra merge roadmap - Monitoring

Blocked by:

• TPA-RFC-77: plan Merge of Tails' and Tor's Pupp... (#41948 - closed)

Notes for a plan:

• Make Tails nodes reachable to Prometheus (add them to the Tails VPN?)