asset-swapper: Exchange Proxy support

[dorothy-zbornak]

Description

This adds a new swap quote consumer to asset-swapper, ExchangeProxySwapQuoteConsumer, which can generate call data for the Exchange Proxy's transformERC20() function.

ExchangeProxySwapQuoteConsumer.getCallDataOrThrowAsync() can accept an options object:

{
  extensionContractOpts: {
    // Whether to accept ETH and automatically wrap it to WETH prior to fill.
    isFromETH: boolean;
    // Whether to unwrap WETH to ETH after the fill.
    isToETH: boolean;
  }
}

The CalldataInfo struct returned by getCallDataOrThrowAsync() from all consumers now has an allowanceTarget field.

Odds and Ends

• Pinned @0x/instant's @0x/asset-swapper dependency to the old version to avoid constantly breaking instant.
• Added transformer data decoding utils to @0x/contracts-zero-ex.
• Add ITransformERC20 contract artifacts/wrappers where necessary.
• Added placeholder EP addresses to ContractAddresses. None of this stuff is deployed so they're all NULL for now.
• Fix @0x/contracts-broker tests and add them to CI.
• Allow for identifiers prefixed with underscores in python contract wrappers.

Testing instructions

Types of changes

Checklist:

• Prefix PR title with [WIP] if necessary.
• Add tests to cover changes as needed.
• Update documentation as needed.
• Add new entries to the relevant CHANGELOG.jsons.

[coveralls]

Coverage decreased (-0.03%) to 79.658% when pulling 7cf9630 on feat/asset-swapper/exchange-proxy-support into ecfbd62 on feat/contracts-zero-ex/0x-api-erc20-transformers.

[dorothy-zbornak]

🧷

[dekz]

This could also technically be MAX_UINT256 as well right? As it's defined as what is actually sent in value?

[dorothy-zbornak]

No, because we don't want to wrap the protocol fee.