lib: externalized messages support

@nodejs/ctc @nodejs/collaborators ...

externalizing the error and output messages in lib

• the approach taken here is derived from the template string based mechanism described here
• this is an alternative approach to the ICU based approach that I am working on in https://github.com/nodejs/node/pull/3413

This introduces a new internal/messages module that exports a template string tag function. The externalized messages are in internal/messages_en.js for now but can be moved to a different location.

Within the lib src, we can use this mechanism using tagged template strings:

const I18N = require('internal/messages');

const foo = 'testing';
throw new Error(I18N`Example error: ${foo}`);

In the messages_en.js file, we'd have something like:

{
  ...,
  "Example error: {0}": {
    "key": "ERR000009"
  },
  ...
}

The template string would expand into:

ERR000009: Example Error: testing

Later on, when we get into actually translating messages, we would have other message_{locale}.js files (or however else we'd like to separate it out) that would look something like:

{
  ...,
  "Example error: {0}": {
    "key": "ERR000009",
    "value": "Ejemplo de error: {0}"
}

I'm not yet convinced this approach is ideal, but it's functional. There are a few gotchas with template strings currently that are less than ideal (e.g. line wrapping issues, lookup is a bit inefficient).

Getting this out now, tho, to solicit input on the approach.

This is still a work in progress