fix(house_keeper): Emit the correct circuit_id for aggregation round 2 (

#547)

## What ❔

This is us hardcoding the circuit_id to 2 for aggregation_round 2. This
fix is useless as soon as we change the config (not expected anytime
soon).

A real fix will follow where we address what is saved in database layer
and this patch will be removed altogether.

## Why ❔

This is necessary to enable autoscaler to work (emits the correct data
for prover groups, which in turn can be picked by autoscaler).

## Checklist

- [x] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [ ] Tests for the changes have been added / updated.
- [ ] Documentation comments have been added / updated.
- [x] Code has been formatted via `zk fmt` and `zk lint`.

core/lib/zksync_core/src/house_keeper/fri_prover_queue_monitor.rs

@@ -34,6 +34,19 @@ impl PeriodicJob for FriProverStatsReporter {
         let stats = conn.fri_prover_jobs_dal().get_prover_jobs_stats().await;
 
         for ((circuit_id, aggregation_round), stats) in stats.into_iter() {
+            // BEWARE, HERE BE DRAGONS.
+            // In database, the circuit_id stored is the circuit for which the aggregation is done,
+            // not the circuit which is running.
+            // There is a single node level aggregation circuit, which is circuit 2.
+            // This can aggregate multiple leaf nodes (which may belong to different circuits).
+            // This reporting is a hacky forced way to use circuit_id 2 which will solve autoscalers.
+            // A proper fix will be later provided to solve this at database level.
+            let circuit_id = if aggregation_round == 2 {
+                2
+            } else {
+                circuit_id
+            };
+
             let group_id = self
                 .config
                 .get_group_id_for_circuit_id_and_aggregation_round(circuit_id, aggregation_round)