This PR makes `chai` and `should()` _globals_ when using Mocha:
- `chai` is configured with `chai-as-promised`
- A `.mocharc.js` requires `./test/setup.js` _from the monorepo root_.
- Updated the ESLint config to recognize the globals.
- Updated Wallaby config
All instances of `import chai...` and the like have been removed from all test files.
