Install nested packages from Yarn cache before running build tests

[bvaughn]

Unblocks #21641

We cache the root node_modules directory on Circle CI and restore it before e.g. running tests. We don't cache nested node_modules folders though, instead choosing to re-install (from the local Yarn cache) after restoring the root cache. We were not doing this for the yarn_test_build targets though which caused problems if there were dependency differences between packages.

This PR addresses that.

[gaearon]

oof

[sizebot]

Comparing: c96761c...00e7076

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	=	127.20 kB	127.20 kB	=	40.76 kB	40.76 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	130.01 kB	130.01 kB	=	41.67 kB	41.67 kB
facebook-www/ReactDOM-prod.classic.js	=	404.75 kB	404.75 kB	=	74.83 kB	74.83 kB
facebook-www/ReactDOM-prod.modern.js	=	393.15 kB	393.15 kB	=	73.08 kB	73.07 kB
facebook-www/ReactDOMForked-prod.classic.js	=	404.75 kB	404.75 kB	=	74.83 kB	74.83 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against 00e7076