[Flight] Cache the value if we visit the same I/O or Promise multiple times along different paths

[sebmarkbage]

We avoid visiting the same async node twice but if we see it again we returned "null" indicating that there's no I/O there.

This means that if you have two different Promises both resolving from the same I/O node then we only show one of them. However, in general we treat that as two different I/O entries to allow for things like batching to still show up separately.

This fixes that by caching the return value for multiple visits. So if we found I/O (but no user space await) in one path and then we visit that path through a different Promise chain, then we'll still emit it twice.

However, if we visit the same exact Promise that we emitted an await on then we skip it. Because there's no need to emit two awaits on the same thing. It only matters when the path ends up informing whether it has I/O or not.

[react-sizebot]

Comparing: 0fa3250...515b922

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	=	605.41 kB	605.41 kB	=	107.21 kB	107.22 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	=	664.38 kB	664.38 kB	=	117.09 kB	117.09 kB
facebook-www/ReactDOM-prod.classic.js	=	688.25 kB	688.25 kB	=	121.13 kB	121.13 kB
facebook-www/ReactDOM-prod.modern.js	=	678.67 kB	678.67 kB	=	119.49 kB	119.49 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

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