Refactor away from opaque hashes (#5226)

* System.BlockHash

* Fix hash

* Introduce K/V iteration in all _concat maps

Also move across:
- System.Account (blake2_128_concat)
- Balances.Locks (twox_64_concat)
- ElectionsPhragmen.VotesOf (twox_64_concat)
- ElectionsPhragmen.StakeOf (twox_64_concat)
- Identity.IdentityOf (twox_64_concat)
- Identity.SubsOf (twox_64_concat)
- Society.Payouts (twox_64_concat)
- Session.NextKeys (twox_64_concat)
- Identity.SuperOf (blake2_128_concat)
- Session.KeyOwner (blake2_128_concat)
- Society.SuspendedCandidates (twox_64_concat)
- Society.SuspendedMembers (twox_64_concat)
- Society.Vouching (twox_64_concat)
- Society.Strikes (twox_64_concat)
- System.EventTopics
- Balances.Account

* Build fixes

* Ensure migration happens in correct order

* Staking.*

* Vesting.* Offences.*

* Democracy.*

* Babe.* Collective.*

* Grandpa.*

* Assets.* Benchmark.* Contracts.* Elections.* Asset.* Nicks.*

Also introduce real account list

* ImOnline.*

* Treasury.*

* Recovery.*

* Final bits.

* Docs

* Fix one test

* Fix test

* All passing except the UI tests

* Remove linked_map part 1

* Remove linked_map

* Some iterator utils for double maps.

* Remove old migrations

* Introduce tombstone for LinkedMap type

* Migration for genesis hash

* Fix build

* Fix hash

* Rename Map is_linked -> unused, keeping backwards compat (#5256)

* Update frame/balances/src/lib.rs

Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com>

* Update frame/elections/src/lib.rs

Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com>

* Remove old migration code.

* Update frame/system/src/lib.rs

Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com>

* Update bin/node/runtime/src/lib.rs

Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com>

* Fix hash

* fix session migration

* Fix watning

Co-authored-by: Jaco Greeff <jacogr@gmail.com>
Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Robert Habermeier <rphmeier@gmail.com>

substrate/frame/contracts/src/lib.rs

@@ -98,7 +98,6 @@ mod rent;
 
 #[cfg(test)]
 mod tests;
-mod migration;
 
 use crate::exec::ExecutionContext;
 use crate::account_db::{AccountDb, DirectAccountDb};
@@ -667,10 +666,6 @@ decl_module! {
 		fn on_finalize() {
 			GasSpent::kill();
 		}
-
-		fn on_runtime_upgrade() {
-			migration::on_runtime_upgrade::<T>()
-		}
 	}
 }
 
@@ -934,13 +929,13 @@ decl_storage! {
 		/// Current cost schedule for contracts.
 		CurrentSchedule get(fn current_schedule) config(): Schedule = Schedule::default();
 		/// A mapping from an original code hash to the original code, untouched by instrumentation.
-		pub PristineCode: map hasher(blake2_256) CodeHash<T> => Option<Vec<u8>>;
+		pub PristineCode: map hasher(identity) CodeHash<T> => Option<Vec<u8>>;
 		/// A mapping between an original code hash and instrumented wasm code, ready for execution.
-		pub CodeStorage: map hasher(blake2_256) CodeHash<T> => Option<wasm::PrefabWasmModule>;
+		pub CodeStorage: map hasher(identity) CodeHash<T> => Option<wasm::PrefabWasmModule>;
 		/// The subtrie counter.
 		pub AccountCounter: u64 = 0;
 		/// The code associated with a given account.
-		pub ContractInfoOf: map hasher(blake2_256) T::AccountId => Option<ContractInfo<T>>;
+		pub ContractInfoOf: map hasher(twox_64_concat) T::AccountId => Option<ContractInfo<T>>;
 		/// The price of one unit of gas.
 		GasPrice get(fn gas_price) config(): BalanceOf<T> = 1.into();
 	}