Fix hardcoded path to codegen cli for monorepos (#35430)
Fix hardcoded path to codegen cli for monorepos (#35430)

Summary:
Fixes https://github.com/facebook/react-native/issues/35429

This fix is fairly straightforward. Instead of hardcoding two separate paths for this repo or a simple user's project, we ask Node to resolve `react-native-codegen`.

Because `react-native-codegen` is moved [into the `/packages/*` folder](https://github.com/facebook/react-native/blob/main/package.json#L104), it's part of a workspace in this repository. That means that this fix works not only for monorepos in general but also resolves the right path within the react native repository.

You can test this out yourself when running this command in either the root, or any other workspace in this repository:
```bash
node --print "require('path').dirname(require.resolve('react-native-codegen/package.json'))"
```

I've tested this on Node 16 and 18, and seems to work nicely. Note that you _**have to specify `react-native-codegen/package.json`**_. That's because the `react-native-codegen` package itself is technically invalid; it's missing an entry point within the package (no `main`). When running `node --print "require.resolve('react-native-codegen')"` Node can't resolve the main entry point, and will fail during this process.

## Changelog

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[iOS] [Fixed] - Fix incorrect codegen CLI paths in monorepo projects

Pull Request resolved: https://github.com/facebook/react-native/pull/35430

Test Plan: See PR https://github.com/facebook/react-native/issues/35429

Reviewed By: cortinico

Differential Revision: D41475878

Pulled By: cipolleschi

fbshipit-source-id: f0c362b64cf9c3543a3a031d7eaf302c1314e3f0

facebook/react-native,facebook/react-native,facebook/react-native,facebook/react-native,facebook/react-native,facebook/react-native,facebook/react-native,facebook/react-native,facebook/react-native