grandpa: report equivocations with unsigned extrinsics (#6656)

* grandpa: use unsigned extrinsics for equivocation reporting

* grandpa: allow signed reports as well

* grandpa: change runtime api for submitting unsigned extrinsics

* grandpa: fix tests

* grandpa: add test for unsigned validation

* grandpa: add benchmark for equivocation proof checking

* offences: fix grandpa benchmark

* grandpa: add proper weight for equivocation reporting extrinsic

* grandpa: fix weight unit

Author: andresilva

benchmarking/src/lib.rs

@@ -282,21 +282,16 @@ benchmarks! {
 	}
 
 	report_offence_grandpa {
-		let r in 1 .. MAX_REPORTERS;
 		let n in 0 .. MAX_NOMINATORS.min(MAX_NOMINATIONS as u32);
-		let o = 1;
 
-		// Make r reporters
-		let mut reporters = vec![];
-		for i in 0 .. r {
-			let reporter = account("reporter", i, SEED);
-			reporters.push(reporter);
-		}
+		// for grandpa equivocation reports the number of reporters
+		// and offenders is always 1
+		let reporters = vec![account("reporter", 1, SEED)];
 
 		// make sure reporters actually get rewarded
 		Staking::<T>::set_slash_reward_fraction(Perbill::one());
 
-		let (mut offenders, raw_offenders) = make_offenders::<T>(o, n)?;
+		let (mut offenders, raw_offenders) = make_offenders::<T>(1, n)?;
 		let keys = ImOnline::<T>::keys();
 
 		let offence = GrandpaEquivocationOffence {
@@ -316,9 +311,9 @@ benchmarks! {
 		assert_eq!(
 			System::<T>::event_count(), 0
 			+ 1 // offence
-			+ 2 * r // reporter (reward + endowment)
-			+ o // offenders slashed
-			+ o * n // nominators slashed
+			+ 2 // reporter (reward + endowment)
+			+ 1 // offenders slashed
+			+ n // nominators slashed
 		);
 	}