Benchmark Timestamp Pallet (#4891)

* Add selected_benchmark! macro.

* Use selected_benchmark! in Identity pallet.

* Implement timestamp pallet benchmark.

* Fix some nits.

* Bump impl_version.

substrate/bin/node/runtime/src/lib.rs

@@ -82,7 +82,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
 	spec_version: 216,
-	impl_version: 0,
+	impl_version: 1,
 	apis: RUNTIME_API_VERSIONS,
 };
 
@@ -813,6 +813,7 @@ impl_runtime_apis! {
 		{
 			match module.as_slice() {
 				b"pallet-identity" | b"identity" => Identity::run_benchmark(extrinsic, steps, repeat).ok(),
+				b"pallet-timestamp" | b"timestamp" => Timestamp::run_benchmark(extrinsic, steps, repeat).ok(),
 				_ => return None,
 			}
 		}