ZeroEx: TransformERC20, TokenSpender (#2545)

* `@0x/contracts-utils`: Convert more 0.6 contracts

* `@0x/contracts-erc20`: Add solidity 0.6 contracts.

* `@0x/utils`: Add new `ZeroExRevertErrors` revert types

* `@0x/contracts-zero-ex`: Introduce the `TransformERC20` feature.

* `@0x/subproviders`: Update ganache-core.
`@0x/web3-wrapper`: Update ganache-core.

* `@0x/contracts-zero-ex`: Make `TokenSpender`'s puppet contract a distinct contract type and rename `getTokenSpenderPuppet()` to `getAllowanceTarget()`

* `@0x/zero-ex`: Rebase and use "slot" instead of "offset" language in storage buckets.

* `@0x/web3-wrapper`: Add `getAccountNonceAsync()` to `Web3Wrapper`

* `@0x/contracts-zero-ex`: Revamp TransformERC20.

* `@0x/contracts-zero-ex`: Remove `payable` from `IERC20Transformer.transform()` and disable hex capitalization linter rule because of prettier conflicts.

* `@0x/contracts-zero-ex`: Use `immutable` owner in `Puppet` instead of `Ownable`.

* `@x/utils`: Address review feedback.

* `@0x/contracts-zero-ex`: Address review feedback.

* `@0x/contracts-utils`: Address review feedback.

* `@0x/contracts-zero-ex`: Return deployment nonce in `transform()`.

* `@0x/contracts-zero-ex`: Finish returning deployment nonce in `transform()`.

* `@0x/contracts-zero-ex`: Fix doc-gen bug.

* `@0x/contracts-zero-ex`: Address review comments.

* `@0x/utils`: Add `NegativeTransformERC20OutputERror`

* `@0x/contracts-zero-ex`: Revert if the taker's output amount decreases.

Co-authored-by: Lawrence Forman <me@merklejerk.com>

contracts/zero-ex/src/index.ts

@@ -36,3 +36,4 @@ export {
     TupleDataItem,
     StateMutability,
 } from 'ethereum-types';
+export { rlpEncodeNonce } from './nonce_utils';