Remove assetDataUtils everywhere (#2373)

* remove assetDataUtils everywhere

* export IAssetDataContract from @0x/contract-wrappers to allow @0x/instant to decode asset data  synchronously

* export generic function `decodeAssetDataOrThrow` and add ERC20Bridge support

* export `hexUtils` from order-utils instead of contracts-test-utils

contracts/test-utils/src/index.ts

@@ -27,17 +27,6 @@ export { OrderFactory } from './order_factory';
 export { bytes32Values, testCombinatoriallyWithReferenceFunc, uint256Values } from './combinatorial_utils';
 export { TransactionFactory } from './transaction_factory';
 export { testWithReferenceFuncAsync } from './test_with_reference';
-export {
-    hexConcat,
-    hexHash,
-    hexLeftPad,
-    hexInvert,
-    hexSlice,
-    hexRandom,
-    hexRightPad,
-    hexSize,
-    toHex,
-} from './hex_utils';
 export {
     BatchMatchOrder,
     ContractName,