Composite accounts (#4820)

* Basic account composition.

* Add try_mutate_exists

* De-duplicate

* Refactor away the UpdateBalanceOutcome

* Expunge final UpdateBalanceOutcome refs

* Refactor transfer

* Refactor reservable currency stuff.

* Test with the alternative setup.

* Fixes

* Test with both setups.

* Fixes

* Fix

* Fix macros

* Make indices opt-in

* Remove CreationFee, and make indices opt-in.

* Fix construct_runtime

* Fix last few bits

* Fix tests

* Update trait impls

* Don't hardcode the system event

* Make tests build and fix some stuff.

* Pointlessly bump runtime version

* Fix benchmark

* Another fix

* Whitespace

* Make indices module economically safe

* Migrations for indices.

* Fix

* Whilespace

* Trim defunct migrations

* Remove unused storage item

* More contains_key fixes

* Docs.

* Bump runtime

* Remove unneeded code

* Fix test

* Fix test

* Update frame/balances/src/lib.rs

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

* Fix ED logic

* Repatriate reserved logic

* Typo

* Fix typo

* Update frame/system/src/lib.rs

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

* Update frame/system/src/lib.rs

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

* Last few fixes

* Another fix

* Build fix

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Jaco Greeff <jacogr@gmail.com>
Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

substrate/frame/contracts/src/lib.rs

@@ -401,9 +401,6 @@ pub trait Trait: frame_system::Trait {
 	/// to removal of a contract.
 	type SurchargeReward: Get<BalanceOf<Self>>;
 
-	/// The fee required to create an account.
-	type CreationFee: Get<BalanceOf<Self>>;
-
 	/// The fee to be paid for making a transaction; the base.
 	type TransactionBaseFee: Get<BalanceOf<Self>>;
 
@@ -517,9 +514,6 @@ decl_module! {
 		/// to removal of a contract.
 		const SurchargeReward: BalanceOf<T> = T::SurchargeReward::get();
 
-		/// The fee required to create an account.
-		const CreationFee: BalanceOf<T> = T::CreationFee::get();
-
 		/// The fee to be paid for making a transaction; the base.
 		const TransactionBaseFee: BalanceOf<T> = T::TransactionBaseFee::get();
 
@@ -966,7 +960,6 @@ pub struct Config<T: Trait> {
 	pub max_depth: u32,
 	pub max_value_size: u32,
 	pub contract_account_instantiate_fee: BalanceOf<T>,
-	pub account_create_fee: BalanceOf<T>,
 }
 
 impl<T: Trait> Config<T> {
@@ -978,7 +971,6 @@ impl<T: Trait> Config<T> {
 			max_depth: T::MaxDepth::get(),
 			max_value_size: T::MaxValueSize::get(),
 			contract_account_instantiate_fee: T::ContractFee::get(),
-			account_create_fee: T::CreationFee::get(),
 		}
 	}
 }