Add Chilled event to staking chill extrinsics (#9250)

* Add `Chilled` event to staking chill extrinsics

* Update do_remove_{nom, val} doc comments

* Not working: trying to match on event

* Account for chilled event in offences benchmarking

* trigger ci

* correct

substrate/frame/staking/src/lib.rs

@@ -1329,6 +1329,9 @@ pub mod pallet {
 		Kicked(T::AccountId, T::AccountId),
 		/// The election failed. No new era is planned.
 		StakingElectionFailed,
+		/// An account has stopped participating as either a validator or nominator.
+		/// \[stash\]
+		Chilled(T::AccountId),
 	}
 
 	#[pallet::error]
@@ -2523,8 +2526,11 @@ impl<T: Config> Pallet<T> {
 
 	/// Chill a stash account.
 	fn chill_stash(stash: &T::AccountId) {
-		Self::do_remove_validator(stash);
-		Self::do_remove_nominator(stash);
+		let chilled_as_validator = Self::do_remove_validator(stash);
+		let chilled_as_nominator = Self::do_remove_nominator(stash);
+		if chilled_as_validator || chilled_as_nominator {
+			Self::deposit_event(Event::<T>::Chilled(stash.clone()));
+		}
 	}
 
 	/// Actually make a payment to a staker. This uses the currency's reward function
@@ -3014,10 +3020,15 @@ impl<T: Config> Pallet<T> {
 
 	/// This function will remove a nominator from the `Nominators` storage map,
 	/// and keep track of the `CounterForNominators`.
-	pub fn do_remove_nominator(who: &T::AccountId) {
+	///
+	/// Returns true if `who` was removed from `Nominators`, otherwise false.
+	pub fn do_remove_nominator(who: &T::AccountId) -> bool {
 		if Nominators::<T>::contains_key(who) {
 			Nominators::<T>::remove(who);
 			CounterForNominators::<T>::mutate(|x| x.saturating_dec());
+			true
+		} else {
+			false
 		}
 	}
 
@@ -3034,10 +3045,15 @@ impl<T: Config> Pallet<T> {
 
 	/// This function will remove a validator from the `Validators` storage map,
 	/// and keep track of the `CounterForValidators`.
-	pub fn do_remove_validator(who: &T::AccountId) {
+	///
+	/// Returns true if `who` was removed from `Validators`, otherwise false.
+	pub fn do_remove_validator(who: &T::AccountId) -> bool {
 		if Validators::<T>::contains_key(who) {
 			Validators::<T>::remove(who);
 			CounterForValidators::<T>::mutate(|x| x.saturating_dec());
+			true
+		} else {
+			false
 		}
 	}
 }