test,module: add test for exports cjs loader check

Refs: https://github.com/nodejs/node/pull/31001#issuecomment-576353389

PR-URL: https://github.com/nodejs/node/pull/31427


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Shelley Vohr <codebytere@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>