Why: Because they are the approved standard by TC39 and Ecma for
JavaScript modules.
Changes:
* Wrap mw-node-qunit in run.js to register babel to transpile modules
for node v6
* Change all sources in src/ to use ES modules
* Change constants.js to be able to run without
jQuery.bracketedDevicePixelRatio given ES modules are hoisted to
the top by spec so we can't patch globals before importing it
* Change all tests in tests/node-qunit/ to use ES modules
* Drop usage of mock-require given ES modules are easy to stub with
sinon
Additional changes:
* Rename tests/node-qunit/renderer.js to renderer.test.js to follow
the convention of all the other files
* Make npm run test:node run only .test.js test files so that it
doesn't run the stubs.js or run.js file.
Bug: T171951
Change-Id: I17a0b76041d5e2fd18e2d54950d9d7c0db99a941
