Fixes TotalValueLocked out of sync in nomination pools (#3052)

The `TotalLockedValue` storage value in nomination pools pallet may get
out of sync if the staking pallet does implicit withdrawal of unlocking
chunks belonging to a bonded pool stash. This fix is based on a new
method in the `OnStakingUpdate` traits, `on_withdraw`, which allows the
nomination pools pallet to adjust the `TotalLockedValue` every time
there is an implicit or explicit withdrawal from a bonded pool's stash.

This PR also adds a migration that checks and updates the on-chain TVL
if it got out of sync due to the bug this PR fixes.

**Changes to `trait OnStakingUpdate`**

In order for staking to notify the nomination pools pallet that chunks
where withdrew, we add a new method, `on_withdraw` to the
`OnStakingUpdate` trait. The nomination pools pallet filters the
withdraws that are related to bonded pool accounts and updates the
`TotalValueLocked` accordingly.

**Others**
- Adds try-state checks to the EPM/staking e2e tests
- Adds tests for auto withdrawing in the context of nomination pools

**To-do**
- [x] check if we need a migration to fix the current `TotalValueLocked`
(run try-runtime)
- [x] migrations to fix the current on-chain TVL value 

 ✅ **Kusama**:
```
TotalValueLocked: 99.4559 kKSM
TotalValueLocked (calculated) 99.4559 kKSM
```
⚠️ **Westend**:
```
TotalValueLocked: 18.4060 kWND
TotalValueLocked (calculated) 18.4050 kWND
```
**Polkadot**: TVL not released yet.

Closes https://github.com/paritytech/polkadot-sdk/issues/3055

---------

Co-authored-by: command-bot <>
Co-authored-by: Ross Bulat <ross@parity.io>
Co-authored-by: Dónal Murray <donal.murray@parity.io>

substrate/frame/nomination-pools/src/mock.rs

@@ -134,11 +134,24 @@ impl sp_staking::StakingInterface for StakingMock {
 
 	fn withdraw_unbonded(who: Self::AccountId, _: u32) -> Result<bool, DispatchError> {
 		let mut unbonding_map = UnbondingBalanceMap::get();
+
+		// closure to calculate the current unlocking funds across all eras/accounts.
+		let unlocking = |pair: &Vec<(EraIndex, Balance)>| -> Balance {
+			pair.iter()
+				.try_fold(Zero::zero(), |acc: Balance, (_at, amount)| acc.checked_add(*amount))
+				.unwrap()
+		};
+
 		let staker_map = unbonding_map.get_mut(&who).ok_or("Nothing to unbond")?;
+		let unlocking_before = unlocking(&staker_map);
 
 		let current_era = Self::current_era();
+
 		staker_map.retain(|(unlocking_at, _amount)| *unlocking_at > current_era);
 
+		// if there was a withdrawal, notify the pallet.
+		Pools::on_withdraw(&who, unlocking_before.saturating_sub(unlocking(&staker_map)));
+
 		UnbondingBalanceMap::set(&unbonding_map);
 		Ok(UnbondingBalanceMap::get().is_empty() && BondedBalanceMap::get().is_empty())
 	}