Test for suspending with modern strict mode

[rickhanlonii]

Overview

Adds a test to show the cause of an infinite loop in Relay related to these effects in Relay and useModernStrictMode. The bug is related to effect behavior when committing trees that re-suspend after initial mount.

With useModernStrictEffect, when you:

• initial mount
• update
• suspend (to fallbacks)
• resolve
• re-commit

We fire strict effects during the second mount, like it's a new tree. This creates weird cases, where if there was an update while we suspended, we'll first fire only the effects that changed dependencies, and then fire strict effects.

Creating a test to demonstrate the behavior to see if it's a bug.

[react-sizebot]

Comparing: 64f354c...e831878

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	=	177.10 kB	177.10 kB	=	55.20 kB	55.20 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	177.64 kB	177.64 kB	=	55.53 kB	55.53 kB
facebook-www/ReactDOM-prod.classic.js	=	594.34 kB	594.34 kB	=	104.96 kB	104.96 kB
facebook-www/ReactDOM-prod.modern.js	=	577.60 kB	577.60 kB	=	102.02 kB	102.02 kB
test_utils/ReactAllWarnings.js	Deleted	66.60 kB	0.00 kB	Deleted	16.28 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	66.60 kB	0.00 kB	Deleted	16.28 kB	0.00 kB

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