Removal of modules polyfill for ember-source 3.27+ breaks production builds for all apps using registerWaiter

[runspired]

Offending imports:

import { registerWaiter, unregisterWaiter } from '@ember/test';

These imports are missing in non-test env production builds leading the build to break. This includes all versions of EmberData, meaning that a large share of apps running ember-source 3.27 are unable to ship to production

I believe this worked prior to 3.27 because the transformation of registerWaiter to Ember.registerWaiter meant no import was present, and therefore registerWaiter being undefined did not break anything as apps typically wrap usage of it in if (DEBUG) {} or if (Ember.testing) {}.

[runspired]

The source of the error is this build step here: https://github.com/emberjs/ember.js/blob/master/lib/index.js#L225-L228

Which filters all ember-testing paths out of the build. @ember/test remains in the build but when accessed will fail because it re-exports from ember-testing https://github.com/emberjs/ember.js/blob/master/packages/%40ember/test/index.js#L1-L11

[rwjblue]

I think this was fixed by emberjs/ember.js#19540, but happy to reopen if that is incorrect.

[allthesignals]

Not sure why but even even on 3.28.11 of ember-source, I'm still seeing this issue:

allthesignals/labs-zola@74ed883