Update file extensions for Node TS support

[RDIL]

What's the problem this PR addresses?

Fixes #6595

How did you fix it?

Always consider mts as ESM and cts as CJS

Checklist

• I have read the Contributing Guide.

• I have set the packages that need to be released for my changes to be effective.

• I will check that all automated PR checks pass before the PR gets reviewed.

[adrian-gierakowski]

Anything stopping progress on this PR?

[RDIL]

Sorry @adrian-gierakowski, completely forgot to follow up here.

[merceyz]

This PR needs tests to ensure it works and that we don't regress on it.

[goloveychuk]

to make strip types works, you need to change pnp mjs loader and chain other loaders , because (assumption is) types stripes is implemented as loader also.
#6595 (comment)

[goloveychuk]

test with simple type cast ( as any) could written to validates this

[goloveychuk]

@RDIL can we finish this pls?

[goloveychuk]

return {
    format,
    source: format === `commonjs` ? void 0 : await fs.promises.readFile(filePath, `utf8`),
    shortCircuit: false
  };

should be replaced with return nextLoad(urlString, context, nextLoad);
because typescript types striping is done by loader.
So, probably, pnp loader should hack fs and and then just chain other loaders without explicit loading files.
@arcanis wdyt?

[RDIL]

@goloveychuk sorry, i'm super busy these days, but if you want to grab my commits and make a new PR, I'm happy to review

[RDIL]

Closing in favor of #6763