improve naming for (nested) bundled SSR page and API route entry points to better reflect original file based routing name

[thescientist13]

Summary

Coming out of #1223 / #1224 was the realization that nested SSR page bundles, in particular those with the name route based file name, e.g.

src/
  pages/
    blog/
      index.js

Will get the following top level bundle names from Rollup due to the repeated index.js files in this case

public/
  _index.js
  _index2.js
  _index3.js
  ...

Details

While in the PR this was fixed by leveraging the bundle names created by Rollup and updating outputPath on the route object in the graph, it would be better if the naming was more reflective of the source route name path, e.g.

public/
  _index.js
  _blog-index.js

Or output based on path

public/
  blog/
    _index.js
  _index.js

Notes:

• This would require some sort of renaming within the bundling process in Rollup perhaps?
• Should also deeply test for nested API routes and influence better graph properties as part of #1167

[thescientist13]

This was kind of done in #1236