Histogram support in runtime metrics (#6935)

* Histogram support in runtime metrics

Add support for histograms to the runtime metrics. Additionally add
`polkadot_parachain_verify_dispute_signature` histogram which tracks the
time needed from the runtime to verify a single validator signature of a
dispute statement.

* Add noops

* u64 instead of f64

* Update buckets

* Wrap `get_current_time()` in runtime metrics

* Change the dimension of the Histogram from usec to sec

* Fix a compilation error

* Update buckets

* Fix `on_signature_check_complete` calculation

* Update buckets

* Update buckets

* formatting

* Another weights update

* Adjust buckets again

* Final buckets adjustment

* Revert "Fix a compilation error"

This reverts commit 06290b40a39eeb78de2602d8916a39edf7a8b714.

* Update primitives/src/v4/metrics.rs

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

* Use `saturating_sub` for time difference calculation

* Pass nanoseconds to client instead of seconds (using f64 in runtime is dangerous)

---------

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

polkadot/primitives/src/v4/metrics.rs

@@ -27,6 +27,8 @@ pub enum RuntimeMetricOp {
 	IncrementCounterVec(u64, RuntimeMetricLabelValues),
 	/// Increment a counter metric by value.
 	IncrementCounter(u64),
+	/// Observe histogram value
+	ObserveHistogram(u128),
 }
 
 /// Runtime metric update event.
@@ -127,6 +129,16 @@ pub mod metric_definitions {
 		pub labels: &'a [&'static str],
 	}
 
+	/// `Histogram` metric definition
+	pub struct HistogramDefinition<'a> {
+		/// The name of the metric.
+		pub name: &'static str,
+		/// The description of the metric.
+		pub description: &'static str,
+		/// The buckets for the histogram
+		pub buckets: &'a [f64],
+	}
+
 	/// Counts parachain inherent data weights. Use `before` and `after` labels to differentiate
 	/// between the weight before and after filtering.
 	pub const PARACHAIN_INHERENT_DATA_WEIGHT: CounterVecDefinition = CounterVecDefinition {
@@ -176,4 +188,12 @@ pub mod metric_definitions {
 			description: "Counts the number of bitfields signature checked in `enter_inner`.",
 			labels: &["validity"],
 		};
+
+	/// Measures how much time does it take to verify a single validator signature of a dispute statement
+	pub const PARACHAIN_VERIFY_DISPUTE_SIGNATURE: HistogramDefinition =
+		HistogramDefinition {
+			name: "polkadot_parachain_verify_dispute_signature",
+			description: "How much time does it take to verify a single validator signature of a dispute statement, in seconds",
+			buckets: &[0.0, 0.00005, 0.00006, 0.0001, 0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.3, 0.5, 1.0],
+	};
 }