dillon1000/react

[DevTools] Make Devtools Regression Build (#24599)

This PR adds a script that downloads the specified react version from NPM (ie. react-dom, react, and react-test-renderer) and replaces the corresponding files in the build folder with the downloaded react files.

The scheduler package, unlike react-dom, react, and react-test-renderer, is versioned differently, so we also need to specifically account for that in the script.