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/collective/src/lib.rs

@@ -106,10 +106,10 @@ decl_storage! {
 		pub Proposals get(fn proposals): Vec<T::Hash>;
 		/// Actual proposal for a given hash, if it's current.
 		pub ProposalOf get(fn proposal_of):
-			map hasher(blake2_256) T::Hash => Option<<T as Trait<I>>::Proposal>;
+			map hasher(identity) T::Hash => Option<<T as Trait<I>>::Proposal>;
 		/// Votes on a given proposal, if it is ongoing.
 		pub Voting get(fn voting):
-			map hasher(blake2_256) T::Hash => Option<Votes<T::AccountId, T::BlockNumber>>;
+			map hasher(identity) T::Hash => Option<Votes<T::AccountId, T::BlockNumber>>;
 		/// Proposals so far.
 		pub ProposalCount get(fn proposal_count): u32;
 		/// The current members of the collective. This is stored sorted (just by value).
@@ -168,6 +168,17 @@ decl_error! {
 	}
 }
 
+mod migration {
+	use super::*;
+
+	pub fn migrate<T: Trait<I>, I: Instance>() {
+		for p in Proposals::<T, I>::get().into_iter() {
+			ProposalOf::<T, I>::migrate_key_from_blake(&p);
+			Voting::<T, I>::migrate_key_from_blake(&p);
+		}
+	}
+}
+
 // Note: this module is not benchmarked. The weights are obtained based on the similarity of the
 // executed logic with other democracy function. Note that councillor operations are assigned to the
 // operational class.
@@ -177,6 +188,10 @@ decl_module! {
 
 		fn deposit_event() = default;
 
+		fn on_runtime_upgrade() {
+			migration::migrate::<T, I>();
+		}
+
 		/// Set the collective's membership.
 		///
 		/// - `new_members`: The new member list. Be nice to the chain and
@@ -535,7 +550,7 @@ mod tests {
 		type Version = ();
 		type ModuleToIndex = ();
 		type AccountData = ();
-		type OnNewAccount = ();
+		type MigrateAccount = (); type OnNewAccount = ();
 		type OnKilledAccount = ();
 	}
 	impl Trait<Instance1> for Test {