Remove Evented mixin. Use native EventTarget.

[BobrImperator]

• Removes Evented Mixin
  This is a prerequisite to making everything ES6 classes and make it easier to convert to Typescript.

Mostly keeps the API the same except for the fact that we extend the Native EventTarget and emit CustomEvents which require to provide data as a detail field.

Event handlers must change from

  authenticator.on('sessionDataUpdated', data => {

to

 authenticator.on('sessionDataUpdated', ({ detail: data }) => {

Additionally, not the whole Evented API is implemented on the Authenticator, Store and InternalSession objects.
Only on, off and trigger methods are supported.

Currently I'm not convinced that the events are needed but also don't see a need to refactor away.

Lastly, I've discovered a different behavior of the internal-session.js once the ObjectProxy was refactored to ES6 such as export default class InternalSession extends ObjectProxy {} as opposed to the current classic syntax export default ObjectProxy.extend({}), for some reason set,get and setProperties calls proxying misbehave when the methods are implemented outside the extend({}) body.

[github-actions]

Some tests with 'continue-on-error: true' have failed:

• test-esa test:one ember-beta

• test-app test:one ember-canary

• classic-test-app test:one ember-beta

• test-app test:one ember-beta

• test-esa test:one ember-canary

  Created by continue-on-error-comment

[github-actions]

Some tests with 'continue-on-error: true' have failed:

• classic-test-app test:one ember-canary

Created by continue-on-error-comment