Performance: avoid triggering map deopt in V8

[romgrk]

The shape of the objects changed by this PR are both created in 2 locations with 2 different shapes, which most JS engines won't like. I've noticed this in particular in V8 while benchmarking production code.

react/packages/react-reconciler/src/ReactFiberCacheComponent.js

Lines 66 to 77 in 1293047

	export const CacheContext: ReactContext<Cache> = enableCache
	? {
	$$typeof: REACT_CONTEXT_TYPE,
	// We don't use Consumer/Provider for Cache components. So we'll cheat.
	Consumer: (null: any),
	Provider: (null: any),
	// We'll initialize these at the root.
	_currentValue: (null: any),
	_currentValue2: (null: any),
	_threadCount: 0,
	}
	: (null: any);

react/packages/react-reconciler/src/ReactFiberHostContext.js

Lines 47 to 54 in 1293047

	export const HostTransitionContext: ReactContext<TransitionStatus | null> = {
	$$typeof: REACT_CONTEXT_TYPE,
	_currentValue: null,
	_currentValue2: null,
	_threadCount: 0,
	Provider: (null: any),
	Consumer: (null: any),
	};

react/packages/react-reconciler/src/ReactFiberHooks.js

Lines 3530 to 3531 in 1293047

	useLayoutEffect: mountLayoutEffect,
	useInsertionEffect: mountInsertionEffect,

react/packages/react-reconciler/src/ReactFiberHooks.js

Lines 3492 to 3493 in 1293047

	useInsertionEffect: throwInvalidHookError,
	useLayoutEffect: throwInvalidHookError,

[react-sizebot]

Comparing: 1293047...a27ad7a

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	=	176.83 kB	176.83 kB	=	54.91 kB	54.90 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	173.55 kB	173.55 kB	=	54.11 kB	54.11 kB
facebook-www/ReactDOM-prod.classic.js	=	594.16 kB	594.16 kB	=	104.42 kB	104.41 kB
facebook-www/ReactDOM-prod.modern.js	=	577.42 kB	577.42 kB	=	101.45 kB	101.45 kB
test_utils/ReactAllWarnings.js	Deleted	66.87 kB	0.00 kB	Deleted	16.36 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	66.87 kB	0.00 kB	Deleted	16.36 kB	0.00 kB

Generated by 🚫 dangerJS against a27ad7a

[kassens]

Thank you, we should probably install a "sort properties in object literals" lint rule to catch these generally.