Optimization: Exclude package.json files not used in resolution.

[ryan-roemer]

It's a very odd case, but if there's something like:

// index.js
// package.json
{
  main: "bad.js"
}

Then we Node will resolve to index.js and we won't need package.json at all.

Additionally, if package.json resolves to ., ./, index, index.js|mjs, etc. we could just exclude it as without it we get the same resolution rules.