errors: print original exception context

[bcoe]

When --enable-source-maps is set, the error context displayed
above the stack trace now shows original source rather than
transpiled.

When --enable-source-maps is set, annotate the top of the stack trace with the original source, rather than the ugly transpiled source:

before:

  if ((obj === null || obj === void 0 ? void 0 : (_obj$a = obj.a) === null || _obj$a === void 0 ? void 0 : _obj$a.b) === 22) throw Error('an exception');

after:

/Users/bencoe/oss/node-1/test/fixtures/source-map/babel-throw-original.js:18
  if (obj?.a?.b === 22) throw Error('an exception');

Open questions

The logic in node_errors.cc is a little magical to me, specifically I'm trying to figure out how it's placing the ^ under the throw, rather than under the Error (which is where the stack trace points).

@addaleax I know you've also worked in this file, any thoughts (maybe this is an issue we don't care about).

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines