size audit of aio-cli node_modules, improvement suggestions

Only listing those with at least double digit sizes in megabytes, and only for a production build via `npm i --production`.
Total size of `node_modules` is `466M`

```
$ du | sort -nr | cut -f2- | xargs du -hs
466M .
144M ./@parcel
128M ./@parcel/transformer-js
68M ./aws-sdk
32M ./aws-sdk/clients
17M ./aws-sdk/dist
17M ./rxjs
16M ./yeoman-environment
16M ./yeoman-environment/node_modules
15M ./aws-sdk/apis
15M ./@adobe
11M ./yeoman-environment/node_modules/rxjs
```

`@parcel/transformer-js` is the biggest, mainly because it includes pre-built native binding `.node` files for all the platforms. This can be optimized by not including `.node` files that are not used by the current platform. There is nothing we can do however to affect this, since the `.node` files are packed into the tarball for the package version, and not compiled post-install per platform. The linux `.node` files themselves contribute `90M`. Parcel is used in the app plugin for `aio app run`.

`aws-sdk` is used in @adobe/aio-lib-web which is in turn used by the app plugin for deploy/undeploy (for S3 only). This is v2 of the sdk - we can improve this if we move to v3 where each service has its own package, and we only use S3.

`yeoman-environment` is used by the app plugin, to run the yeoman generators when creating an app. The bulk of it is rxjs@7.

`rxjs` is used by multiple modules - events plugin (events-lib), inquirer (cli UI). v6 is 17M.