- adds support for:
  - JSON based GenesisConfig (patch/full-config) to ChainSpec allowing
    interaction with runtime GenesisBuilder API.
  - interacting with arbitrary runtime wasm blob to chain-spec-builder command line util,
  - GenesisBuilder API in kitchensink runtime
- removes `code` from system_pallet
- adds `code` to the ChainSpec
- deprecates ChainSpec::from_genesis, but also changes the signature of
  this method extending it with code argument. ChainSpec::builder()
  should be used instead.
- implements GenesisBuilder API for node-template-runtime and kitchensink-runtime.

Squash commit of work made in: paritytech/substrate#14562

- all references to `RuntimeGenesisConfig` in node/service are removed,
- `RococoGenesisExt` is removed. It was the hack to allow overwriting
  `EpochDurationInBlocks`. Removal of `RococGenesisExt` prevents from
manipulating the state to change the runtime constants, what allows to
keep metadata const.
- 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,
- rococo-runtime changes:
  -- Explicit building of fast-runtime version of rococo-runtime is no longer done.
  -- Environment variables which control the time::EpochDurationInBlocks value were added:
    `ROCOCO_FAST_RUNTIME` - enables the fast runtime version of
    runtime with default value of EpochDurationInBlocks set to 10. Value of
    env does not matter.
    `ROCOCO_EPOCH_DURATION` - enables the fast runtime version with
    provided value of EpochDurationInBlocks (epoch duration will be set to
    the value of env).

    Examples:
    - to build runtime for `versi_staging_testnet_config which had
      EpochDurationInBlocks set to 100:
    ```
    ROCOCO_EPOCH_DURATION=100 cargo build -p rococo
    ```
    - to build runtime for `versi_staging_testnet_config which had
      EpochDurationInBlocks set to 100:
    ```
    ROCOCO_EPOCH_DURATION=100 cargo build -p rococo-runtime
    ```
    - to build runtime for `wococo_development`
    ```
    ROCOCO_EPOCH_DURATION=10 cargo build -p rococo-runtime
    or
    ROCOCO_FAST_RUNTIME=1 cargo build -p rococo-runtime
    ```
- ChainSpec: tests against legacy added

- integration-tests: storages building migrated to GenesisConfig JSON patches
- parachain-template: GenesisBuilder implemented + JSON patch in ChainSpec
- parachains/runtimes: GenesisBuilder API implemented
- chain-specs: RuntimeGenesisConfig removed, JSON patches added
- json_vs_legacy_tests: tests for json-based ChainSpecs added
    Copy of current chain_spec files (using deprecated from_genesis) was
    created in order to test json-patching vs old from_genesis version.
- chain-specs: code moved from pallet_system to ChainSpec

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This reverts commit a247f58.

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This reverts commit 6bfc04d.

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Co-authored-by: Javier Viola <javier@parity.io>

Co-authored-by: Davide Galassi <davxy@datawok.net>

Co-authored-by: Davide Galassi <davxy@datawok.net>

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Co-authored-by: Kevin Krone <kevin@parity.io>

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Co-authored-by: Davide Galassi <davxy@datawok.net>

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