[draft] Use concurrent root in RTR

[jackpope]

Based on

• https://github.com/facebook/react/pull/28497
• https://github.com/facebook/react/pull/28489
• https://github.com/facebook/react/pull/28419

Summary

How did you test this change?

[react-sizebot]

Comparing: 1f9befef5c6045c6f65f5c667d83fbe6ab025d81...a5b7ae13d0ebdea0988a5c04011f6ba6d1488575

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	=	175.91 kB	175.91 kB	=	54.53 kB	54.53 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	172.39 kB	172.39 kB	=	53.70 kB	53.70 kB
facebook-www/ReactDOM-prod.classic.js	=	589.86 kB	589.86 kB	=	103.60 kB	103.60 kB
facebook-www/ReactDOM-prod.modern.js	=	573.39 kB	573.39 kB	=	100.66 kB	100.66 kB
test_utils/ReactAllWarnings.js	Deleted	64.83 kB	0.00 kB	Deleted	16.08 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	64.83 kB	0.00 kB	Deleted	16.08 kB	0.00 kB

Generated by :no_entry_sign: dangerJS against a5b7ae13d0ebdea0988a5c04011f6ba6d1488575