module exports are typed as `any`, which can cause missed type errors

Given a Relay generated file such as:

```javascript
/**
* @flow
*/

// ...

/*::
export type Foo = {| ... |}
*/

// ...

(node/*: any*/).hash = '...';
module.exports = node;
```

I _think_ that this `any` type for `node` should be reconsidered, as it seems to introduce `any`s in awry import statements:

```javascript
import type { Foo, Bar } from "./__generated__/File.graphql.js"
```

`yarn flow` does not catch the unknown `Bar` type here, instead it gets typed as `any`. Normally you would expect an error like:

```
Cannot import Bar because there is no Bar export in ./__generated__/File.graphql.js
```

I believe this is because the `module.exports` value is typed to `any`, and the `any`s leak:

```javascript
const a: any = {}
const b = a.Bar
b // <- this is of type `any`
```

Start with the Relay-generated JavaScript example and run yarn flow against an import of an unknown type such as Bar. Trace how the module.exports value and its any annotation affect named type imports; done means Flow reports that an unexported type cannot be imported instead of treating it as any.

Written by the indexing model from the issue text.