babel-polyfill generation

The babelrc wizard can generate custom babel polyfill configurations that only include the required apis. This should be separate from the main babelrc and npm install generated content so the user can just ignore it.

Start at the babelrc wizard's generation flow and trace how the main babelrc and npm install content are produced. Define the separate custom polyfill output so it includes only required APIs and can be ignored independently, then verify the generated configurations do not mix these contents.

Written by the indexing model from the issue text.