refactor: Transaction-Payment module (#3816)

* Initial draft that compiles

* Extract payment stuff from balances

* Extract multiplier update stuff from system

* Some fixes.

* Update len-fee as well

* some review comments.

* Remove todo

* bump

substrate/srml/generic-asset/src/lib.rs

@@ -1056,7 +1056,6 @@ impl<T: Subtrait> system::Trait for ElevatedTrait<T> {
 	type MaximumBlockWeight = T::MaximumBlockWeight;
 	type MaximumBlockLength = T::MaximumBlockLength;
 	type AvailableBlockRatio = T::AvailableBlockRatio;
-	type WeightMultiplierUpdate = ();
 	type BlockHashCount = T::BlockHashCount;
 	type Version = T::Version;
 }

substrate/srml/generic-asset/src/mock.rs

@@ -56,7 +56,6 @@ impl system::Trait for Test {
 	type Lookup = IdentityLookup<u64>;
 	type Header = Header;
 	type Event = TestEvent;
-	type WeightMultiplierUpdate = ();
 	type MaximumBlockWeight = MaximumBlockWeight;
 	type MaximumBlockLength = MaximumBlockLength;
 	type AvailableBlockRatio = AvailableBlockRatio;