--cwd option for Yarn Workspaces compatibility

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[AWS Amplify Console repository](https://github.com/aws-amplify/amplify-console/issues)

**Is your feature request related to a problem? Please describe.**
I want to call the Amplify CLI from a location that doesn't contain the `amplify/` directory, i.e. in project root `/`, where the Amplify config for the project might be in `workspaces/amplify`.

**Describe the solution you'd like**
I'd like Amplify CLI to mimic `yarn --cwd [dir]` option, which would resolve the problem above with `amplify --cwd workspaces/ [command]`.

**Describe alternatives you've considered**
Moving everything into the root directory of the project, but that's less organized and versatile than the functionality I'm requesting.

**Additional context**
https://github.com/aws-amplify/amplify-console/issues/1750#issuecomment-821728324