feat[devtools]: add package for fusebox integration

[hoxyq]

Summary

Stacked on https://github.com/facebook/react/pull/28552. Review only the last commit at the top.

These changes add new package react-devtools-fusebox, which is the entrypoint for the RDT Frontend, which will be used in Chrome DevTools panel. The main differences from other frontend shells (extension, standalone) are:

1. This package builds scripts in ESM format, this is required by Chrome DevTools, see webpack config: https://github.com/facebook/react/blob/c69952f1bf6e23252d47e0f7eb98efbbb2cc2c55/packages/react-devtools-fusebox/webpack.config.frontend.js#L50-L52
2. The build includes styles in a separate .css file, which is required for Chrome DevTools: styles are loaded lazily once panel is mounted.

[react-sizebot]

Comparing: d012a32f840cf575b9d07bf1ed96af34af99e060...2204347fae842c67b54d061680d9360e0bd8fa3a

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	=	168.76 kB	168.76 kB	=	52.91 kB	52.91 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	170.57 kB	170.57 kB	=	53.44 kB	53.44 kB
facebook-www/ReactDOM-prod.classic.js	=	590.84 kB	590.84 kB	=	103.91 kB	103.91 kB
facebook-www/ReactDOM-prod.modern.js	=	566.66 kB	566.66 kB	=	100.10 kB	100.10 kB
test_utils/ReactAllWarnings.js	Deleted	64.44 kB	0.00 kB	Deleted	16.10 kB	0.00 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
test_utils/ReactAllWarnings.js	Deleted	64.44 kB	0.00 kB	Deleted	16.10 kB	0.00 kB

Generated by :no_entry_sign: dangerJS against 2204347fae842c67b54d061680d9360e0bd8fa3a