test for unusual error cases: verify that module require()
falls back to index if package.json names a missing file and
throws an error if package.json is unparseable.
PR-URL: https://github.com/nodejs/node/pull/23285
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
