feat: add performed pool state updates metric (#3714)

crates/transaction-pool/src/metrics.rs

@@ -33,6 +33,9 @@ pub struct TxPoolMetrics {
 
     /// Number of all transactions of all sub-pools: pending + basefee + queued
     pub(crate) total_transactions: Gauge,
+
+    /// How often the pool was updated after the canonical state changed
+    pub(crate) performed_state_updates: Counter,
 }
 
 /// Transaction pool maintenance metrics

crates/transaction-pool/src/pool/txpool.rs

@@ -261,6 +261,8 @@ impl<T: TransactionOrdering> TxPool<T> {
         // update the metrics after the update
         self.update_size_metrics();
 
+        self.metrics.performed_state_updates.increment(1);
+
         OnNewCanonicalStateOutcome { block_hash, mined: mined_transactions, promoted, discarded }
     }