[regression Canary] Ember.EXTEND_PROTOTYPES is undefined

[mixonic]

In #16467 Ember.EXTEND_PROTOTYPES was removed from the framework. Common libraries like ember-inflector use this value (source) and we need to have an intimate API deprecation cycle here.

For example:

Object.defineProperty(Ember, 'EXTEND_PROTOTYPES', {
  enumerable: false,
  get() {
    deprecate('Accessing Ember.EXTEND_PROTOTYPES is deprecated, please migrate to Ember.ENV.EXTEND_PROTOTYPES');
    return ENV.EXTEND_PROTOTYPES;
  }
});

(where the value used to be set: source)

/cc @rwjblue