Ignore function and symbol values on custom-elements on the server

[sebmarkbage]

Follow up from: #21153 (comment)

[sizebot]

Comparing: 9ed0167...74597fd

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	=	122.65 kB	122.65 kB	=	39.35 kB	39.36 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	129.21 kB	129.21 kB	=	41.43 kB	41.43 kB
facebook-www/ReactDOM-prod.classic.js	=	405.89 kB	405.89 kB	=	75.39 kB	75.39 kB
facebook-www/ReactDOM-prod.modern.js	=	394.15 kB	394.15 kB	=	73.53 kB	73.53 kB
facebook-www/ReactDOMForked-prod.classic.js	=	405.89 kB	405.89 kB	=	75.39 kB	75.39 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
facebook-www/ReactDOMServer-prod.modern.js	+0.24%	47.46 kB	47.58 kB	+0.14%	11.05 kB	11.06 kB
facebook-www/ReactDOMServer-prod.classic.js	+0.24%	48.33 kB	48.44 kB	+0.13%	11.26 kB	11.28 kB
oss-stable/react-dom/cjs/react-dom-server.browser.production.min.js	+0.22%	20.10 kB	20.15 kB	+0.12%	7.55 kB	7.56 kB
oss-stable/react-dom/umd/react-dom-server.browser.production.min.js	+0.22%	20.28 kB	20.32 kB	+0.08%	7.61 kB	7.62 kB
oss-stable/react-dom/cjs/react-dom-server.node.production.min.js	+0.21%	20.53 kB	20.58 kB	+0.12%	7.71 kB	7.72 kB
oss-experimental/react-dom/cjs/react-dom-server.browser.production.min.js	+0.21%	20.66 kB	20.70 kB	+0.17%	7.66 kB	7.67 kB
oss-experimental/react-dom/umd/react-dom-server.browser.production.min.js	+0.21%	20.84 kB	20.88 kB	+0.06%	7.73 kB	7.73 kB
oss-experimental/react-dom/cjs/react-dom-server.node.production.min.js	+0.21%	21.09 kB	21.13 kB	+0.12%	7.82 kB	7.83 kB

Generated by 🚫 dangerJS against 74597fd