[Float] add tests for resource emission when rendering no head or just a head

[gnoff]

Added a couple tests to cover cases where resources are used when not rendering an entire document.

[sizebot]

Comparing: 618388b...4507517

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	=	135.46 kB	135.46 kB	=	43.44 kB	43.44 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	148.00 kB	148.00 kB	=	47.33 kB	47.33 kB
facebook-www/ReactDOM-prod.classic.js	=	491.72 kB	491.72 kB	=	87.50 kB	87.50 kB
facebook-www/ReactDOM-prod.modern.js	=	477.00 kB	477.00 kB	=	85.27 kB	85.27 kB
facebook-www/ReactDOMForked-prod.classic.js	=	491.72 kB	491.72 kB	=	87.50 kB	87.50 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against 4507517