[DevTools] Make Devtools Regression Build

[lunaruan]

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.

[sizebot]

Comparing: 5a1e558...49c8a8c

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-stable/react-dom/cjs/react-dom.production.min.js	=	131.49 kB	131.49 kB	=	42.14 kB	42.15 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	136.75 kB	136.75 kB	=	43.70 kB	43.70 kB
facebook-www/ReactDOM-prod.classic.js	=	441.13 kB	441.13 kB	=	80.41 kB	80.41 kB
facebook-www/ReactDOM-prod.modern.js	=	426.42 kB	426.42 kB	=	78.24 kB	78.24 kB
facebook-www/ReactDOMForked-prod.classic.js	=	441.13 kB	441.13 kB	=	80.41 kB	80.42 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against 49c8a8c