Introduce __defineNonEnumerable hook, this allows parts of ember to opt-out of the enumerable safety. Unfortunately at this time there is not way to create fast non-enumerable properties. Historically ember has this to allow people to merge, extend and JSON.stringify. Unfortunately some things like Ember.Views should do not need this but still suffer from the pretty hefty overhead.

This PR Reduces the cost of view allocation by 300% -> 400%.

Micro bench (creating 10,000 views):

before: 120ms
after:   35ms
[FEATURE "ember-routing-transitioning-classes”]

Disables eager URL updates during slow transitions in favor of new CSS
classes added to `link-to`s (in addition to `active` class):

- `transitioning-in`: link-to is not currently active, but will be
  when the current underway (slow) transition completes.
- `transitioning-out`: link-to is currently active, but will no longer
  be active when the current underway (slow) transition completes.
Merge pull request #9919 from machty/transitioning-classes

[FEATURE "ember-routing-transitioning-classes”]
[FEATURE] Revert ember-routing-will-change-hooks
[FEATURE] Revert ember-routing-handlebars-action-with-key-code
[FEATURE] Revert ember-runtime-item-controller-inline-class.
[FEATURE] Revert event-dispatcher-can-disable-event-manager.
[FEATURE ember-routing-transitioning-classes] namespace classes

Use .ember-transitioning-in and .ember-transitioning-out
instead of non-ember-namespaced classes.
Merge pull request #9984 from rwjblue/revert-features

Revert features that are no longer in the proper direction.
[FEATURE ember-routing-transitioning-classes] enable this feature
Merge pull request #9987 from machty/ember-transitioning-in

[FEATURE ember-routing-transitioning-classes] namespace classes
Bump up emberjs-build version

Testing with the latest version of emberjs-build
Stream-based shouldDisplay checking

Closes #9895.
Merge pull request #9988 from ef4/fix-inline-if

Stream-based shouldDisplay checking
Cleanup escaping in SimpleBoundView
[BUGFIX release] Fix hasThis lookup regression

Also optimizes lookup using lastIndexOf(x, 0), resulting in a constant time lookup
Merge pull request #9991 from kanongil/this-path-fix

Fix hasThis lookup regression
Refactor the `if` helper to not rely on `bind` anymore
Merge pull request #9995 from mmun/cleanup-escaping

Cleanup escaping in SimpleBoundView
Merge pull request #9997 from ebryn/bound-if-view

Refactor the `if` helper to not rely on `bind` anymore