[refactor] move isValidElementType to react-is

[rickhanlonii]

After owner stacks, we don't check this in ReactJSX, so it's really only used in react-is and memo. Neither of these are really accurate long term, because renderers can define their own element type.

So for memo I'm just changing it to a nullish check, which will allow custom renderer elements to be wrapped in memo, so we can move this to react-is so nothing internally starts using it.

[react-sizebot]

Comparing: 7943da1...972400f

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	+0.05%	1.83 kB	1.83 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	517.29 kB	517.29 kB	=	92.26 kB	92.26 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	=	617.58 kB	617.58 kB	=	109.52 kB	109.52 kB
facebook-www/ReactDOM-prod.classic.js	=	653.67 kB	653.67 kB	=	115.18 kB	115.18 kB
facebook-www/ReactDOM-prod.modern.js	=	643.95 kB	643.95 kB	=	113.59 kB	113.59 kB
facebook-www/React-dev.classic.js	=	55.47 kB	54.28 kB	=	12.08 kB	11.93 kB
facebook-www/React-dev.modern.js	=	55.47 kB	54.28 kB	=	12.08 kB	11.92 kB
oss-experimental/react/cjs/react.react-server.development.js	=	35.96 kB	35.12 kB	=	8.49 kB	8.38 kB
oss-stable/react/cjs/react.react-server.development.js	=	28.93 kB	28.13 kB	=	6.95 kB	6.84 kB
oss-stable-semver/react/cjs/react.react-server.development.js	=	28.90 kB	28.11 kB	=	6.92 kB	6.82 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
facebook-www/ReactIs-dev.classic.js	=	6.58 kB	6.49 kB	=	1.42 kB	1.40 kB
facebook-www/ReactIs-dev.modern.js	=	6.58 kB	6.49 kB	=	1.42 kB	1.40 kB
facebook-www/ReactIs-prod.classic.js	=	5.98 kB	5.89 kB	=	1.39 kB	1.37 kB
facebook-www/ReactIs-prod.modern.js	=	5.98 kB	5.89 kB	=	1.39 kB	1.37 kB
facebook-react-native/react/cjs/React-dev.js	=	51.27 kB	50.48 kB	=	11.42 kB	11.31 kB
oss-stable/react/cjs/react.development.js	=	45.27 kB	44.48 kB	=	10.29 kB	10.18 kB
oss-stable-semver/react/cjs/react.development.js	=	45.24 kB	44.45 kB	=	10.27 kB	10.16 kB
oss-experimental/react/cjs/react.development.js	=	47.01 kB	46.17 kB	=	10.65 kB	10.54 kB
facebook-react-native/react-is/cjs/ReactIs-dev.js	=	5.31 kB	5.21 kB	=	1.20 kB	1.18 kB
facebook-react-native/react-is/cjs/ReactIs-prod.js	=	4.77 kB	4.68 kB	=	1.17 kB	1.15 kB
facebook-react-native/react-is/cjs/ReactIs-profiling.js	=	4.77 kB	4.68 kB	=	1.17 kB	1.15 kB
oss-experimental/react-is/cjs/react-is.development.js	=	5.16 kB	5.06 kB	=	1.15 kB	1.13 kB
oss-stable-semver/react-is/cjs/react-is.development.js	=	5.12 kB	5.02 kB	=	1.15 kB	1.13 kB
oss-stable/react-is/cjs/react-is.development.js	=	5.12 kB	5.02 kB	=	1.15 kB	1.13 kB
oss-experimental/react-is/cjs/react-is.production.js	=	4.61 kB	4.52 kB	=	1.10 kB	1.09 kB
oss-stable-semver/react-is/cjs/react-is.production.js	=	4.56 kB	4.47 kB	=	1.10 kB	1.08 kB
oss-stable/react-is/cjs/react-is.production.js	=	4.56 kB	4.47 kB	=	1.10 kB	1.08 kB
facebook-www/React-dev.classic.js	=	55.47 kB	54.28 kB	=	12.08 kB	11.93 kB
facebook-www/React-dev.modern.js	=	55.47 kB	54.28 kB	=	12.08 kB	11.92 kB
oss-experimental/react/cjs/react.react-server.development.js	=	35.96 kB	35.12 kB	=	8.49 kB	8.38 kB
oss-stable/react/cjs/react.react-server.development.js	=	28.93 kB	28.13 kB	=	6.95 kB	6.84 kB
oss-stable-semver/react/cjs/react.react-server.development.js	=	28.90 kB	28.11 kB	=	6.92 kB	6.82 kB

Generated by 🚫 dangerJS against 972400f

[rickhanlonii]

bump @sebmarkbage