Convert ReactMountDestruction (partially) to createRoot

[eps1lon]

Two tests make no more sense with the new createRoot API since unmounting is always bound to the root instance. These can be removed in the same PR we also remove render and unmountComponentAtNode.

[react-sizebot]

Comparing: feed8f3...00aab3a

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	=	176.24 kB	176.24 kB	=	54.88 kB	54.88 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	178.34 kB	178.34 kB	=	55.52 kB	55.52 kB
facebook-www/ReactDOM-prod.classic.js	=	571.94 kB	571.94 kB	=	100.56 kB	100.56 kB
facebook-www/ReactDOM-prod.modern.js	=	555.70 kB	555.70 kB	=	97.62 kB	97.62 kB
test_utils/ReactAllWarnings.js	Deleted	67.55 kB	0.00 kB	Deleted	16.54 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	67.55 kB	0.00 kB	Deleted	16.54 kB	0.00 kB

Generated by 🚫 dangerJS against 00aab3a

[rickhanlonii]

Do we have a test for if you try to createRoot on a container that React has rendered to? Might be worth checking.

Also curious if we have a test that removes the container passed to createRoot and then we call unmount on the non-existent container.

I know these are kinda unrelated, but as I'm going through these tests we're changing I'm also looking for possible missing tests in similar things for createRoot.

[eps1lon]

Good point. I'll check if we have tests though it wouldn't be a very accurate search. But it does make sense to me to have tests for these cases.

[eps1lon]

Do we have a test for if you try to createRoot on a container that React has rendered to? Might be worth checking.

We have ReactDOMRoot - warns when creating two roots managing the same container. Does that match what you are looking for? We also have a test in the same file if we render into existing markup.

Also curious if we have a test that removes the container passed to createRoot and then we call unmount on the non-existent container.

I added a test if we unmount after something else cleared the container content. We already had a test for updating but not unmounting. Does that match what you were looking for?

[rickhanlonii]

Yup both sound good to me.