misbehavior: report multiple offenses per validator as necessary (#2222)

* use proper descriptive generic type names

* cleanup

* Table stores a list of detected misbehavior per authority

* add Table::drain_misbehaviors_for

* WIP: unify misbehavior types; report multiple misbehaviors per validator

Code checks, but tests don't yet pass.

* update drain_misbehaviors: return authority id as well as specific misbehavior

* enable unchecked construction of Signed structs in tests

* remove test-features feature & unnecessary generic

* fix backing tests

This took a while to figure out, because where we'd previously been
passing around `SignedFullStatement`s, we now needed to construct
those on the fly within the test, to take advantage of the signature-
checking in the constructor. That, in turn, necessitated changing the
iterable type of `drain_misbehaviors` to return the validator index,
and passing that validator index along within the misbehavior report.

Once that was sorted, however, it became relatively straightforward:
just needed to add appropriate methods to deconstruct the misbehavior
reports, and then we could construct the signed statements directly.

* fix bad merge

polkadot/node/subsystem/src/messages.rs

@@ -28,7 +28,7 @@ use polkadot_node_network_protocol::{
 	v1 as protocol_v1, NetworkBridgeEvent, ReputationChange, PeerId,
 };
 use polkadot_node_primitives::{
-	CollationGenerationConfig, MisbehaviorReport, SignedFullStatement, ValidationResult,
+	CollationGenerationConfig, SignedFullStatement, ValidationResult,
 	approval::{BlockApprovalMeta, IndirectAssignmentCert, IndirectSignedApprovalVote},
 };
 use polkadot_primitives::v1::{
@@ -41,6 +41,7 @@ use polkadot_primitives::v1::{
 	ValidatorIndex, ValidatorSignature, InboundDownwardMessage, InboundHrmpMessage,
 	CandidateIndex,
 };
+use polkadot_statement_table::v1::Misbehavior;
 use std::{sync::Arc, collections::btree_map::BTreeMap};
 
 /// Subsystem messages where each message is always bound to a relay parent.
@@ -508,7 +509,7 @@ pub enum ProvisionableData {
 	/// The Candidate Backing subsystem believes that this candidate is valid, pending availability.
 	BackedCandidate(CandidateReceipt),
 	/// Misbehavior reports are self-contained proofs of validator misbehavior.
-	MisbehaviorReport(Hash, MisbehaviorReport),
+	MisbehaviorReport(Hash, ValidatorIndex, Misbehavior),
 	/// Disputes trigger a broad dispute resolution process.
 	Dispute(Hash, ValidatorSignature),
 }