esm: phase two of new esm implementation

This PR updates the current `--experimental-modules` implementation
based on the work of the modules team  and reflects Phase 2 of our
new modules plan.

The largest differences from the current implementation include

* `packge.type` which can be either `module` or `commonjs`
  - `type: "commonjs"`:
    - `.js` is parsed as commonjs
    - default for entry point without an extension is commonjs
  - `type: "module"`:
    - `.js` is parsed as esm
    - does not support loading JSON or Native Module by default
    - default for entry point without an extension is esm
* `--entry-type=[mode]`
  - allows you set the type on entry point.
* A new file extension `.cjs`.
  - this is specifically to support importing commonjs in the
    `module` mode.
  - this is only in the esm loader, the commonjs loader remains
    untouched, but the extension will work in the old loader if you use
    the full file path.
* `--es-module-specifier-resolution=[type]`
  - options are `explicit` (default) and `node`
  - by default our loader will not allow for optional extensions in
    the import, the path for a module must include the extension if
    there is one
  - by default our loader will not allow for importing directories that
    have an index file
  - developers can use `--es-module-specifier-resolution=node` to
    enable the commonjs specifier resolution algorithm
  - This is not a “feature” but rather an implementation for
    experimentation. It is expected to change before the flag is
    removed
* `--experimental-json-loader`
  - the only way to import json when `"type": "module"`
  - when enable all `import 'thing.json'` will go through the
    experimental loader independent of mode
  - based on https://github.com/whatwg/html/issues/4315
* You can use `package.main` to set an entry point for a module
  - the file extensions used in main will be resolved based on the
    `type` of the module

Refs: https://github.com/nodejs/modules/blob/master/doc/plan-for-new-modules-implementation.md
Refs: https://github.com/GeoffreyBooth/node-import-file-specifier-resolution-proposal
Refs: https://github.com/nodejs/modules/pull/180
Refs: https://github.com/nodejs/ecmascript-modules/pull/6
Refs: https://github.com/nodejs/ecmascript-modules/pull/12
Refs: https://github.com/nodejs/ecmascript-modules/pull/28
Refs: https://github.com/nodejs/modules/issues/255
Refs: https://github.com/whatwg/html/issues/4315
Refs: https://github.com/w3c/webcomponents/issues/770
Co-authored-by: Myles Borins <MylesBorins@google.com>
Co-authored-by: John-David Dalton <john.david.dalton@gmail.com>
Co-authored-by: Evan Plaice <evanplaice@gmail.com>
Co-authored-by: Geoffrey Booth <webmaster@geoffreybooth.com>
Co-authored-by: Michaël Zasso <targos@protonmail.com>

PR-URL: https://github.com/nodejs/node/pull/26745
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Ben Coe <bencoe@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/.eslintrc.js b/.eslintrc.js
index 54595a8b74..d3a6c73241 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -38,6 +38,8 @@ module.exports = {
     {
       files: [
         'doc/api/esm.md',
+        'test/es-module/test-esm-type-flag.js',
+        'test/es-module/test-esm-type-flag-alias.js',
         '*.mjs',
         'test/es-module/test-esm-example-loader.js',
       ],