Asset-swapper aggregator utils (#2353)

* `@0x/asset-swapper`: Add ERC20Bridge aggregator library.

* `@0x/asset-swapper`: Finish off `aggregate.ts`.

* `@0x/types`: Add `OrderWithoutDomain` type.

* `@0x/asset-swapper`: Add testing infra for sampler/aggregator.

* `@0x/types`: Add `SignedOrderWithoutDomain` type.

* `@0x/asset-swapper`: Update aggregator to take and return orders with signatures.

* `@0x/asset-swapper`: Fix broken aggregator tests.

* `@0x/asset-swapper`: Pass the sampler contract into aggregator entry points.

* `@0x/contract-artifacts`: Add `IERC20BridgeSampler` artifact.

* `@0x/contract-wrappers`: Add `IERC20BridgeSampler` wrapper.

* `@0x/asset-swapper`: Address review comments.

* fixed testing

* refactored aggregate.ts and embeded into asset-swapper

* added adjusted rates for taker and maker fees

* remove PrunedSignedOrders

* updated contract-addresses and addressed some other todos

* streamlined logic

* patched in lawrences changes

* renamed aggregator utils and removed market_utils.ts

* added ack heartbeats

* fixed bug

* patches

* added dummy order things

* Dummy with valid sig

* Tweak gas price calculation to wei

* added test coverage and fixed bugs

* fixed migrations

* Fix CHANGELOGs and types export

* Deploy latest ERC20BridgeSampler on Mainnet

* `@0x/types` Revert CHANGELOG.

* `@0x/asset-swapper`: Address review comments.
`@0x/contract-addresses`: Make kyber lowercase.

* made protocol fee multiplier async

* `@0x/asset-swapper: Fix build errors and do some code cleanup.

* use assetDataUtils where possible

packages/contract-artifacts/src/index.ts

@@ -23,6 +23,7 @@ import * as WETH9 from '../artifacts/WETH9.json';
 import * as ZRXToken from '../artifacts/ZRXToken.json';
 import * as ERC20BridgeProxy from '../artifacts/ERC20BridgeProxy.json';
 import * as ZrxVault from '../artifacts/ZrxVault.json';
+import * as IERC20BridgeSampler from '../artifacts/IERC20BridgeSampler.json';
 
 export {
     AssetProxyOwner,
@@ -50,4 +51,5 @@ export {
     Staking,
     StakingProxy,
     ZrxVault,
+    IERC20BridgeSampler,
 };