remove OnStakerSlash replace with OnStakingEvents (#14527)

* remove 'OnStakerSlash', replace with 'OnStakingEvents'

* fix other features in pallets

* small fixes

* fix docs

* fix docs

* fix docs

* Update primitives/staking/src/lib.rs

Co-authored-by: Gonçalo Pestana <g6pestana@gmail.com>

---------

Co-authored-by: Gonçalo Pestana <g6pestana@gmail.com>

substrate/frame/staking/src/pallet/impls.rs

@@ -26,8 +26,8 @@ use frame_support::{
 	dispatch::WithPostDispatchInfo,
 	pallet_prelude::*,
 	traits::{
-		Currency, CurrencyToVote, Defensive, DefensiveResult, EstimateNextNewSession, Get,
-		Imbalance, LockableCurrency, OnUnbalanced, TryCollect, UnixTime, WithdrawReasons,
+		Currency, Defensive, DefensiveResult, EstimateNextNewSession, Get, Imbalance,
+		LockableCurrency, OnUnbalanced, TryCollect, UnixTime, WithdrawReasons,
 	},
 	weights::Weight,
 };
@@ -38,6 +38,7 @@ use sp_runtime::{
 	Perbill,
 };
 use sp_staking::{
+	currency_to_vote::CurrencyToVote,
 	offence::{DisableStrategy, OffenceDetails, OnOffenceHandler},
 	EraIndex, SessionIndex, Stake, StakingInterface,
 };
@@ -1568,10 +1569,10 @@ impl<T: Config> SortedListProvider<T::AccountId> for UseNominatorsAndValidatorsM
 	}
 }
 
-// NOTE: in this entire impl block, the assumption is that `who` is a stash account.
 impl<T: Config> StakingInterface for Pallet<T> {
 	type AccountId = T::AccountId;
 	type Balance = BalanceOf<T>;
+	type CurrencyToVote = T::CurrencyToVote;
 
 	fn minimum_nominator_bond() -> Self::Balance {
 		MinNominatorBond::<T>::get()