Zombienet tests - disputes on finalized blocks (#2184)

**Overview:**
Adding an extra malus variant focusing on disputing finalized blocks. It
will:
- wrap around approval-voting
- listen to `OverseerSignal::BlockFinalized` and when encountered start
a dispute for the `dispute_offset`th ancestor
- simply pass through all other messages and signals

Add zombienet tests testing various edgecases:
- disputing freshly finalized blocks
- disputing stale finalized blocks
- disputing eagerly pruned finalized blocks (might be separate PR)

**TODO:**
- [x] Register new malus variant
- [x] Simple pass through wrapper (approval-voting)
- [x] Simple network definition
- [x] Listen to block finalizations
- [x] Fetch ancestor hash
- [x] Fetch session index
- [x] Fetch candidate
- [x] Construct and send dispute message
- [x] zndsl test 1 checking that disputes on fresh finalizations resolve
valid Closes #1365
- [x] zndsl test 2 checking that disputes for too old finalized blocks
are not possible Closes #1364
- [ ] zndsl test 3 checking that disputes for candidates with eagerly
pruned relay parent state are handled correctly #1359 (deferred to a
separate PR)
- [x] Unit tests for new malus variant (testing cli etc)
- [x] Clean/streamline error handling
- [ ] ~~Ensure it tests properly on session boundaries~~

---------

Co-authored-by: Javier Viola <javier@parity.io>
Co-authored-by: Marcin S. <marcin@realemail.net>
Co-authored-by: Tsvetomir Dimitrov <tsvetomir@parity.io>

polkadot/node/malus/src/malus.rs

@@ -36,6 +36,8 @@ enum NemesisVariant {
 	BackGarbageCandidate(BackGarbageCandidateOptions),
 	/// Delayed disputing of ancestors that are perfectly fine.
 	DisputeAncestor(DisputeAncestorOptions),
+	/// Delayed disputing of finalized candidates.
+	DisputeFinalizedCandidates(DisputeFinalizedCandidatesOptions),
 }
 
 #[derive(Debug, Parser)]
@@ -80,6 +82,15 @@ impl MalusCli {
 					finality_delay,
 				)?
 			},
+			NemesisVariant::DisputeFinalizedCandidates(opts) => {
+				let DisputeFinalizedCandidatesOptions { dispute_offset, cli } = opts;
+
+				polkadot_cli::run_node(
+					cli,
+					DisputeFinalizedCandidates { dispute_offset },
+					finality_delay,
+				)?
+			},
 		}
 		Ok(())
 	}
@@ -184,4 +195,39 @@ mod tests {
 			assert!(run.cli.run.base.bob);
 		});
 	}
+
+	#[test]
+	fn dispute_finalized_candidates_works() {
+		let cli = MalusCli::try_parse_from(IntoIterator::into_iter([
+			"malus",
+			"dispute-finalized-candidates",
+			"--bob",
+		]))
+		.unwrap();
+		assert_matches::assert_matches!(cli, MalusCli {
+			variant: NemesisVariant::DisputeFinalizedCandidates(run),
+			..
+		} => {
+			assert!(run.cli.run.base.bob);
+		});
+	}
+
+	#[test]
+	fn dispute_finalized_offset_value_works() {
+		let cli = MalusCli::try_parse_from(IntoIterator::into_iter([
+			"malus",
+			"dispute-finalized-candidates",
+			"--dispute-offset",
+			"13",
+			"--bob",
+		]))
+		.unwrap();
+		assert_matches::assert_matches!(cli, MalusCli {
+			variant: NemesisVariant::DisputeFinalizedCandidates(opts),
+			..
+		} => {
+			assert_eq!(opts.dispute_offset, 13); // This line checks that dispute_offset is correctly set to 13
+			assert!(opts.cli.run.base.bob);
+		});
+	}
 }