feat: add queries to clean lost connections in PGCoordinator (#10938)

Adds cleanup queries to clean out "lost" peer and tunnel state after 24 hours.  We leave this state in the database so that anything trying to connect to the peer can see that it was lost, but clean it up after 24 hours to ensure our table doesn't grow without bounds.

coderd/database/queries/tailnet.sql

@@ -122,6 +122,19 @@ DELETE
 FROM tailnet_coordinators
 WHERE heartbeat_at < now() - INTERVAL '24 HOURS';
 
+-- name: CleanTailnetLostPeers :exec
+DELETE
+FROM tailnet_peers
+WHERE updated_at < now() - INTERVAL '24 HOURS' AND status = 'lost'::tailnet_status;
+
+-- name: CleanTailnetTunnels :exec
+DELETE FROM tailnet_tunnels
+WHERE updated_at < now() - INTERVAL '24 HOURS' AND
+      NOT EXISTS (
+        SELECT 1 FROM tailnet_peers
+        WHERE id = tailnet_tunnels.src_id AND coordinator_id = tailnet_tunnels.coordinator_id
+      );
+
 -- name: UpsertTailnetPeer :one
 INSERT INTO
 	tailnet_peers (