[ci] Add new flags GitHub action

[poteto]

Stack from ghstack (oldest at bottom):

• [ci] Improve parallelism of yarn test #30033
• [ci] Add new yarn test GitHub action #30032
• [ci] Remove circleci yarn_flags job #30030
• -> [ci] Add new flags GitHub action #30029

Copies the existing circleci workflow for yarn flags into GitHub
actions. I didn't remove the circleci job for now just to check for
parity.

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
react-compiler-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jun 21, 2024 5:26pm

[react-sizebot]

Comparing: 5727928...d7da04a

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.js	=	6.68 kB	6.68 kB	=	1.83 kB	1.83 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	497.93 kB	497.93 kB	=	89.26 kB	89.26 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.69 kB	6.69 kB	=	1.83 kB	1.83 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	502.75 kB	502.75 kB	=	89.96 kB	89.96 kB
facebook-www/ReactDOM-prod.classic.js	=	597.17 kB	597.17 kB	=	105.33 kB	105.33 kB
facebook-www/ReactDOM-prod.modern.js	=	571.52 kB	571.52 kB	=	101.27 kB	101.27 kB
test_utils/ReactAllWarnings.js	Deleted	62.88 kB	0.00 kB	Deleted	15.69 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	62.88 kB	0.00 kB	Deleted	15.69 kB	0.00 kB

Generated by 🚫 dangerJS against d7da04a