[fix] Bound staking ledger correctly with MaxUnlockingChunks from configuration (#12343)

* used maxunlockingchunks from config

* mhl MaxUnlockingChunks

* no migration needed

* changes as per requested

* fmt

* fix tests

* fix benchmark

* warning in the doc for abrupt changes in the config

* less unnecessary details in the test

* fix tests

Co-authored-by: mrisholukamba <abdulrazzaqlukamba@gmail.com>
Co-authored-by: parity-processbot <>

substrate/frame/staking/src/lib.rs

@@ -301,7 +301,6 @@ mod pallet;
 
 use codec::{Decode, Encode, HasCompact, MaxEncodedLen};
 use frame_support::{
-	parameter_types,
 	traits::{Currency, Defensive, Get},
 	weights::Weight,
 	BoundedVec, CloneNoBound, EqNoBound, PartialEqNoBound, RuntimeDebugNoBound,
@@ -349,10 +348,6 @@ type NegativeImbalanceOf<T> = <<T as Config>::Currency as Currency<
 
 type AccountIdLookupOf<T> = <<T as frame_system::Config>::Lookup as StaticLookup>::Source;
 
-parameter_types! {
-	pub MaxUnlockingChunks: u32 = 32;
-}
-
 /// Information regarding the active era (era in used in session).
 #[derive(Encode, Decode, RuntimeDebug, TypeInfo, MaxEncodedLen)]
 pub struct ActiveEraInfo {
@@ -465,7 +460,7 @@ pub struct StakingLedger<T: Config> {
 	/// Any balance that is becoming free, which may eventually be transferred out of the stash
 	/// (assuming it doesn't get slashed first). It is assumed that this will be treated as a first
 	/// in, first out queue where the new (higher value) eras get pushed on the back.
-	pub unlocking: BoundedVec<UnlockChunk<BalanceOf<T>>, MaxUnlockingChunks>,
+	pub unlocking: BoundedVec<UnlockChunk<BalanceOf<T>>, T::MaxUnlockingChunks>,
 	/// List of eras for which the stakers behind a validator have claimed rewards. Only updated
 	/// for validators.
 	pub claimed_rewards: BoundedVec<EraIndex, T::HistoryDepth>,