Ignore `handleHeaders` if the row has been normalized

Ignore `handleHeaders` if the row has been normalized

This behavior is desirable when `CSVTransformer` interacts with `CSVNormalizer` or any other transformation which converts the row from `Array<string>` into `Array<Object>`, because it avoids the need to pass `handleHeaders: true` to `CSVTransformer` (which is counterintuitive). It is more accurate to say the header row has been deleted by the transformation and must by re-inserted into the write stream later.

The loosening of the type checking is not a breaking change. Since the row is passed directly to `JSON.parse()`, the fields could have always been type `Object` instead of `string`.