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/grandpa/src/lib.rs

@@ -174,8 +174,9 @@ decl_storage! {
 		/// in the "set" of Grandpa validators from genesis.
 		CurrentSetId get(fn current_set_id) build(|_| fg_primitives::SetId::default()): SetId;
 
-		/// A mapping from grandpa set ID to the index of the *most recent* session for which its members were responsible.
-		SetIdSession get(fn session_for_set): map hasher(blake2_256) SetId => Option<SessionIndex>;
+		/// A mapping from grandpa set ID to the index of the *most recent* session for which its
+		/// members were responsible.
+		SetIdSession get(fn session_for_set): map hasher(twox_64_concat) SetId => Option<SessionIndex>;
 	}
 	add_extra_genesis {
 		config(authorities): AuthorityList;
@@ -183,6 +184,15 @@ decl_storage! {
 	}
 }
 
+mod migration {
+	use super::*;
+	pub fn migrate<T: Trait>() {
+		for i in 0..=CurrentSetId::get() {
+			SetIdSession::migrate_key_from_blake(i);
+		}
+	}
+}
+
 decl_module! {
 	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
 		type Error = Error<T>;
@@ -195,6 +205,10 @@ decl_module! {
 			// FIXME: https://github.com/paritytech/substrate/issues/1112
 		}
 
+		fn on_runtime_upgrade() {
+			migration::migrate::<T>();
+		}
+
 		fn on_initialize() {
 			#[cfg(feature = "migrate-authorities")]
 			Self::migrate_authorities();

substrate/frame/grandpa/src/mock.rs

@@ -66,7 +66,7 @@ impl frame_system::Trait for Test {
 	type Version = ();
 	type ModuleToIndex = ();
 	type AccountData = ();
-	type OnNewAccount = ();
+	type MigrateAccount = (); type OnNewAccount = ();
 	type OnKilledAccount = ();
 }