chore: renamed react-native-codegen to @react-native/codegen (#34804)

Summary:
Renamed react-native-codegen package to react-native/codegen and updated references, without changing the folder name; part of RFC480 (https://github.com/facebook/react-native/issues/34692). Follow-up from https://github.com/facebook/react-native/pull/34578

## Changelog

[General] [Changed] - Renamed react-native-codegen package to react-native/codegen and updated references

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Pull Request resolved: https://github.com/facebook/react-native/pull/34804

Reviewed By: cortinico

Differential Revision: D39883584

Pulled By: hoxyq

fbshipit-source-id: 0ef384b75c6edd248b31e37b8f05f64b4d39ca6f