Migrate balances to Attribute Macro

[AurevoirXavier]

No description provided.

[AurevoirXavier]

2021-04-20 01:53:16 `pallet_timestamp::UnixTime::now` is called at genesis, invalid value returned: 0    
2021-04-20 01:53:16 [#0] 🗳  Finalized election round with compute ElectionCompute::OnChain.    
2021-04-20 01:53:16 [0] 💸 new validator set of size 1 has been processed for era 1    
2021-04-20 01:53:16 [darwinia-claims] Genesis Claims List is Set to EMPTY    
2021-04-20 01:53:16 initializing remote client to "http://pangolin-rpc.darwinia.network"    
2021-04-20 01:53:16 scraping keypairs from remote node http://pangolin-rpc.darwinia.network @ 0x04f3476f6cc491529ac61e8e482187b4d231ef8237b92ecff410599037800e5a    
2021-04-20 01:53:16 downloading data for all modules.    
2021-04-20 01:53:19 extending externalities with 1 manually injected keys    
2021-04-20 01:53:19 injecting a total of 7285 keys    
2021-04-20 01:53:20 Migrating `Instance0Darwinia` to `Ring`...    
2021-04-20 01:53:20 Migrating `Instance1Darwinia` to `Kton`...    
2021-04-20 01:53:20 try-runtime executed without errors. Consumed weight = 1107200000000, total weight = 512000000000000 (0.0021625) 

[AurevoirXavier]

branch s2s require this update.

[AurevoirXavier]

P9 High

@AsceticBear @hackfisher

[hackfisher]

LGTM.

Suggest do secondary check that module storage prefix names are the only storage migrations need to process.