Adding monorepo tests apps

[kiwiupover]

The problems

• The current test setup needs to run against npm 4 because we are swapping node modules at build time. Both npm 5+ and yarn expect node modules to be referenced from a repository or from disk somewhere. Pre npm 5+ node modules in present in the node_modules would be included when npm install is run.

• ember-cli-addon-tests builds uses ember-data@3.8.0 ember-cli-fastboot needs to tests against a wide rage of dependancies

• We need to add tests for an embroider application.

The case for a monorepo

We add test-package applications so we can tests again each of the scenarios ember-cli-fastboot supports. We would add an embroider application and run tests against that app. A number of addons have has success with this approach ember-auto-import being one.

Proposed test structure

I propose that we have singular focused tests and a test-package each of those focuses.

• A classic app with tests for routing and the build tests
• An embroider app with routing and build tests
• Custom apps for a customization we support. Finger printing, output files names, custom html

An alternative could be we have a single custom app with all the customization tested in that application. I don't like this idea because it will be hard to fellow contributors to follow the customizations .

Use github actions

This is a no brainer. Test are much faster.

Here is the same PR on my repo running github actions. kiwiupover#8
I don't know why github actions don't run for a PR from a forked repo.

This PR branches from the monoropo PR #767 and should be merged following the merge of that PR.

I broke down package-json-test.js into separate tests with corresponding test-package applications

Adding test-packages for

• basic-app
• fingerprinted app
• custom html app
• custom output app

@rwjblue @kratiahuja, @SparshithNR and @mansona I would love to hear your thoughts about this approach.

[kiwiupover]

Closing this PR in favor of smaller ones.