Migrate from truffle to test-environment (#2007)

* Sketch

* Migrate all tests to test-env

* Finish migration to test-env

* Add config

* Work on GSN tests

* Migrate to newer test-env version and loader syntax

* Add GSN setup

* Finish test-env migration

* Setup coverage using test-env

* Migrate to npm package

* Fix package.json

* Add compile step to CI

* Add comment on coverage setup

* Remove dependency on @truffle/contract

* Fix package-lock merge

* Fix linter errors

* Upgrade test-environment, depend locally on ganche-coverage

* Improve coverage script

* Improve sign.js API

* Move accounts destructuring to describe block

* Switch to prebuilt ethereumjs-vm package

* Upgrade test-enviroment version

* use workspace in circleci config

* remove unnecessary npx

test/GSN/Context.behavior.js

@@ -1,6 +1,8 @@
+const { contract } = require('@openzeppelin/test-environment');
+
 const { BN, expectEvent } = require('@openzeppelin/test-helpers');
 
-const ContextMock = artifacts.require('ContextMock');
+const ContextMock = contract.fromArtifact('ContextMock');
 
 function shouldBehaveLikeRegularContext (sender) {
   describe('msgSender', function () {