BEEFY: client support for detecting equivocated votes (#13285)

* client/beefy: detect equivocated votes

* client/beefy: make sure to persist state after voting

* client/beefy: drop never-used aux-schema v2 migration

* impl review suggestion

---------

Signed-off-by: Adrian Catangiu <adrian@parity.io>

substrate/primitives/beefy/src/commitment.rs

@@ -77,6 +77,7 @@ where
 		self.validator_set_id
 			.cmp(&other.validator_set_id)
 			.then_with(|| self.block_number.cmp(&other.block_number))
+			.then_with(|| self.payload.cmp(&other.payload))
 	}
 }