Update testing dependencies (ember-qunit, @ember/test-helpers, qunit, qunit-dom)

[rwjblue]

A major version release of the testing libraries is afoot! The goals of the next iteration are:

• Drop support for older unsupported Node versions
• Be more Embroider compatible
• Do less "weird stuff"
• Give versioning control back to applications (aka "do less bad magic")

Concretely, those goals result to the following major changes in ember-qunit@5 :

• Drop support for older Node versions
• Remove usage of APIs that are not Embroider compatible
  • {{content-for usage has been replaced by having the tests/index.html directly include our expected DOM content
  • app.import has been removed in favor of leveraging imports along with ember-auto-import / Embroider to process them
• Move qunit and @ember/test-helpers into project devDependencies (ember-qunit is moving them to be peerDependencies along with some helpful validations and error messages to help guide folks down the path)

---

Roll out work:

• Land and release Add compatibility with ember-qunit@5 mainmatter/qunit-dom#816
• Release Embroider with the fixes from Avoid Testem.hookIntoTestFramework unless QUnit or Mocha are defined. embroider-build/embroider#531
• Release prerelease / beta versions
  • @ember/test-helpers
  • ember-qunit
  • qunit-dom
• Update blueprint Update blueprints with new testing configuration #9340
  • Update app blueprint to include the tests/index.html snippet
  • Update app blueprint to add qunit and @ember/test-helpers to devDependencies
  • Update qunit-dom in the app blueprint
• Release final/stable versions
  • @ember/test-helpers (https://github.com/emberjs/ember-test-helpers/releases/tag/v2.0.0)
  • ember-qunit
  • qunit-dom
• Update blueprint to use final/stable versions

[scalvert]

What can I do to help?

[rwjblue]

FYI - This landed in ember-cli@3.23.0-beta.1.

[bertdeblock]

Anything left to be done or can we close this issue?

[rwjblue]

Thanks @bertdeblock!