Offences report system rework (#13425)

* Experiments with common equivocation trait

* Improved equivocation trait

* Fix grandpa equivocation implementation

* Remove some cruft

* Remove some more cruft

* More generic naming

* Simplification of offences manipilation

* More refactory

* Some prograss with the encapsulation of offence report system

* Finally unit type works as a universal null report system

* Align substrate node code

* Further simplification

* Fix test utils

* Remove not required associated type

* Fix benches

* Rollback to prev field name

* Box big params

* Fix typo

* Remove new tag computation

* Remove default implementations

* Better docs

* Return 'Result' instead of bool

* Change offence report system return types

* Some renaming and documentation

* Improve documentation

* More abstract offence report system

* Rename 'consume_evidence' to 'process_evidence'

* Further docs refinements

* Doc for dummy offence report

* Fix rustdoc

* Fix after master merge

* Apply code review suggestions

* Improve docs

substrate/frame/offences/src/mock.rs

@@ -134,17 +134,17 @@ pub fn offence_reports(kind: Kind, time_slot: u128) -> Vec<OffenceDetails<u64, u
 }
 
 #[derive(Clone)]
-pub struct Offence<T> {
+pub struct Offence {
 	pub validator_set_count: u32,
-	pub offenders: Vec<T>,
+	pub offenders: Vec<u64>,
 	pub time_slot: u128,
 }
 
-impl<T: Clone> offence::Offence<T> for Offence<T> {
+impl offence::Offence<u64> for Offence {
 	const ID: offence::Kind = KIND;
 	type TimeSlot = u128;
 
-	fn offenders(&self) -> Vec<T> {
+	fn offenders(&self) -> Vec<u64> {
 		self.offenders.clone()
 	}
 
@@ -167,5 +167,5 @@ impl<T: Clone> offence::Offence<T> for Offence<T> {
 
 /// Create the report id for the given `offender` and `time_slot` combination.
 pub fn report_id(time_slot: u128, offender: u64) -> H256 {
-	Offences::report_id::<Offence<u64>>(&time_slot, &offender)
+	Offences::report_id::<Offence>(&time_slot, &offender)
 }