fatxpool: metrics for unfiltered timings of inblock events (#10312)

This PR adds a new experimental metric
`substrate_sub_txpool_timing_event_in_block2` for the reliability
dashboard. Unlike the existing `in_block` metric which records timing
only for the first `InBlock` event per transaction, the new `in_block2`
metric records every InBlock event without filtering. This allows
tracking transactions that appear in multiple blocks during chain
reorganizations, providing better visibility into fork-related
transaction behavior. The implementation adds the new histogram to
`EventsHistograms` and updates `handle_status()` to record unfiltered
InBlock events before applying deduplication logic.

This approach should allow for experimenting with new _inblock
confidence_ metric, without affecting the data currently shown on the
Reliability Dashboard.

---------

Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
(cherry picked from commit acd0306)

Author: michalkucharczyk

prdoc/pr_10312.prdoc

@@ -0,0 +1,10 @@
+title: 'fatxpool: metrics for unfiltered timings of inblock events'
+doc:
+- audience: Node Dev
+  description: |-
+    This PR adds a new experimental metric `substrate_sub_txpool_timing_event_in_block2` for the reliability dashboard. Unlike the existing `in_block` metric which records timing only for the first `InBlock` event per transaction, the new `in_block2` metric records every InBlock event without filtering. This allows tracking transactions that appear in multiple blocks during chain reorganizations, providing better visibility into fork-related transaction behavior. The implementation adds the new histogram to `EventsHistograms` and updates `handle_status()` to record unfiltered InBlock events before applying deduplication logic.
+
+    This approach should allow for experimenting with new _inblock confidence_ metric, without affecting the data currently shown on the Reliability Dashboard.
+crates:
+- name: sc-transaction-pool
+  bump: minor

substrate/client/transaction-pool/src/fork_aware_txpool/metrics.rs

@@ -97,6 +97,12 @@ pub struct EventsHistograms {
 	pub broadcast: Histogram,
 	/// Histogram of timings for reporting `TransactionStatus::InBlock` event
 	pub in_block: Histogram,
+	/// Histogram of timings for reporting `TransactionStatus::InBlock` event (unfiltered).
+	///
+	/// This is an experimental feature for reliability dashboard.
+	/// Unlike `in_block`, this metric records every InBlock event, including duplicates
+	/// when the same transaction appears in multiple blocks (e.g., during chain reorgs).
+	pub in_block_forks: Histogram,
 	/// Histogram of timings for reporting `TransactionStatus::Retracted` event
 	pub retracted: Histogram,
 	/// Histogram of timings for reporting `TransactionStatus::FinalityTimeout` event
@@ -155,6 +161,23 @@ impl EventsHistograms {
 				)?,
 				registry,
 			)?,
+			in_block_forks: register(
+				Histogram::with_opts(
+					histogram_opts!(
+						"substrate_sub_txpool_timing_event_in_block_forks",
+						"Histogram of timings for reporting unfiltered InBlock event (experimental feature for reliability dashboard)",
+					)
+					.buckets(
+						[
+							linear_buckets(0.0, 3.0, 20).unwrap(),
+							// requested in #9158
+							vec![60.0, 75.0, 90.0, 120.0, 180.0],
+						]
+						.concat(),
+					),
+				)?,
+				registry,
+			)?,
 			retracted: register(
 				Histogram::with_opts(histogram_opts!(
 					"substrate_sub_txpool_timing_event_retracted",
@@ -584,6 +607,15 @@ where
 	) {
 		let Entry::Occupied(mut entry) = submitted_timestamp_map.entry(hash) else { return };
 		let remove = status.is_final();
+
+		// Record unfiltered in_block_forks metric for EVERY InBlock event
+		if matches!(status, TransactionStatus::InBlock(..)) {
+			let duration = timestamp.duration_since(entry.get().submit_timestamp);
+			metrics.report(|metrics| {
+				metrics.events_histograms.in_block_forks.observe(duration.as_secs_f64())
+			});
+		}
+
 		if let Some(submit_timestamp) = entry.get_mut().update(&status) {
 			metrics.report(|metrics| {
 				metrics