next.js

89b4605f - Vendor `react@experimental` under an `experimentalReact` flag (#47759)

Vendor `react@experimental` under an `experimentalReact` flag (#47759) Next.js includes various feature sets that depend on specific release channels of React. However, our current setup only includes the `next` channel of React, which restricts our ability to integrate with features available on the `experimental` channel. To address this limitation, this pull request introduces the following changes: - Vendors the `react@experimental` version, along with the corresponding `react-dom` and `scheduler` packages. - Modifies the `sync-react` script to also update the `experimental` channel and removes `--version` as they're always synced to the latest now. - Retains the default behavior of using the `next` channel in the `appDir` directory. - Adds an option to switch to the `experimental` channel by setting `experimental.experimentalReact: true` in the configuration. fix NEXT-926 ([link](https://linear.app/vercel/issue/NEXT-926))