chain-spec: getting ready for native-runtime-free world (#1256)

This PR prepares chains specs for _native-runtime-free_  world.

This PR has following changes:
- `substrate`:
  - adds support for:
- JSON based `GenesisConfig` to `ChainSpec` allowing interaction with
runtime `GenesisBuilder` API.
- interacting with arbitrary runtime wasm blob to[
`chain-spec-builder`](https://github.com/paritytech/substrate/blob/3ef576eaeb3f42610e85daecc464961cf1295570/bin/utils/chain-spec-builder/src/lib.rs#L46)
command line util,
- removes
[`code`](https://github.com/paritytech/substrate/blob/3ef576eaeb3f42610e85daecc464961cf1295570/frame/system/src/lib.rs#L660)
from `system_pallet`
  - adds `code` to the `ChainSpec`
- deprecates
[`ChainSpec::from_genesis`](https://github.com/paritytech/substrate/blob/3ef576eaeb3f42610e85daecc464961cf1295570/client/chain-spec/src/chain_spec.rs#L263),
but also changes the signature of this method extending it with `code`
argument.
[`ChainSpec::builder()`](https://github.com/paritytech/substrate/blob/20bee680ed098be7239cf7a6b804cd4de267983e/client/chain-spec/src/chain_spec.rs#L507)
should be used instead.
- `polkadot`:
- all references to `RuntimeGenesisConfig` in `node/service` are
removed,
- all
`(kusama|polkadot|versi|rococo|wococo)_(staging|dev)_genesis_config`
functions now return the JSON patch for default runtime `GenesisConfig`,
  - `ChainSpecBuilder` is used, `ChainSpec::from_genesis` is removed,

- `cumulus`:
  - `ChainSpecBuilder` is used, `ChainSpec::from_genesis` is removed,
- _JSON_ patch configuration used instead of `RuntimeGenesisConfig
struct` in all chain specs.
  
---------

Co-authored-by: command-bot <>
Co-authored-by: Javier Viola <javier@parity.io>
Co-authored-by: Davide Galassi <davxy@datawok.net>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Kevin Krone <kevin@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/frame/system/src/lib.rs

@@ -724,8 +724,6 @@ pub mod pallet {
 	#[derive(frame_support::DefaultNoBound)]
 	#[pallet::genesis_config]
 	pub struct GenesisConfig<T: Config> {
-		#[serde(with = "sp_core::bytes")]
-		pub code: Vec<u8>,
 		#[serde(skip)]
 		pub _config: sp_std::marker::PhantomData<T>,
 	}
@@ -739,7 +737,6 @@ pub mod pallet {
 			<UpgradedToU32RefCount<T>>::put(true);
 			<UpgradedToTripleRefCount<T>>::put(true);
 
-			sp_io::storage::set(well_known_keys::CODE, &self.code);
 			sp_io::storage::set(well_known_keys::EXTRINSIC_INDEX, &0u32.encode());
 		}
 	}