[CLEANUP canary] Remove legacy-each & collection support

For #13127

- Remove {{each itemView=}}
- Remove {{each itemViewClass=}}
- Remove {{each itemController=}}
- Remove {{each tagName=}}
- Remove legacy-each-*
- Remove TransformEachIntoCollection
- Remove `CollectionView`

This was done in order to clean up deprecated features to make the
transition to Glimmer 2 easier, since these features won't need to be
supported by Glimmer 2.

packages/ember-application/lib/system/application.js

@@ -26,7 +26,6 @@ import ApplicationInstance from 'ember-application/system/application-instance';
 import TextField from 'ember-views/views/text_field';
 import TextArea from 'ember-views/views/text_area';
 import Checkbox from 'ember-views/views/checkbox';
-import LegacyEachView from 'ember-views/views/legacy_each_view';
 import LinkToComponent from 'ember-routing-views/components/link-to';
 import RoutingService from 'ember-routing/services/routing';
 import ContainerDebugAdapter from 'ember-extension-support/container_debug_adapter';
@@ -1093,7 +1092,6 @@ Application.reopenClass({
     registry.register('component:-text-field', TextField);
     registry.register('component:-text-area', TextArea);
     registry.register('component:-checkbox', Checkbox);
-    registry.register('view:-legacy-each', LegacyEachView);
     registry.register('component:link-to', LinkToComponent);
 
     // Register the routing service...

packages/ember-htmlbars/lib/env.js

@@ -79,11 +79,9 @@ import elementComponent from 'ember-htmlbars/keywords/element-component';
 import partial from 'ember-htmlbars/keywords/partial';
 import input from 'ember-htmlbars/keywords/input';
 import textarea from 'ember-htmlbars/keywords/textarea';
-import collection from 'ember-htmlbars/keywords/collection';
 import yieldKeyword from 'ember-htmlbars/keywords/yield';
 import legacyYield from 'ember-htmlbars/keywords/legacy-yield';
 import mut, { privateMut } from 'ember-htmlbars/keywords/mut';
-import each from 'ember-htmlbars/keywords/each';
 import readonly from 'ember-htmlbars/keywords/readonly';
 import getKeyword from 'ember-htmlbars/keywords/get';
 
@@ -100,12 +98,10 @@ registerKeyword('yield', yieldKeyword);
 registerKeyword('legacy-yield', legacyYield);
 registerKeyword('mut', mut);
 registerKeyword('@mut', privateMut);
-registerKeyword('each', each);
 registerKeyword('readonly', readonly);
 registerKeyword('get', getKeyword);
 
 if (_Ember.ENV._ENABLE_LEGACY_VIEW_SUPPORT) {
-  registerKeyword('collection', collection);
   registerKeyword('view', view);
 }
 

packages/ember-htmlbars/lib/hooks/create-fresh-scope.js

@@ -25,7 +25,7 @@ import EmptyObject from 'ember-metal/empty_object';
   * If `self` is a view, two special locals are created: `view` and
     `controller`. These locals are legacy semantics.
   * If self has a `hasBoundController` property, it is coming from
-    a legacy form of #with or #each
+    a legacy form of #with
     (`{{#with something controller=someController}}`). This has
     the special effect of giving the child scope the supplied
     `controller` keyword, with an unrelated `self`. This is

packages/ember-htmlbars/lib/index.js

@@ -120,8 +120,6 @@ import eachInHelper from 'ember-htmlbars/helpers/each-in';
 import normalizeClassHelper from 'ember-htmlbars/helpers/-normalize-class';
 import concatHelper from 'ember-htmlbars/helpers/concat';
 import joinClassesHelper from 'ember-htmlbars/helpers/-join-classes';
-import legacyEachWithControllerHelper from 'ember-htmlbars/helpers/-legacy-each-with-controller';
-import legacyEachWithKeywordHelper from 'ember-htmlbars/helpers/-legacy-each-with-keyword';
 import htmlSafeHelper from 'ember-htmlbars/helpers/-html-safe';
 import hashHelper from 'ember-htmlbars/helpers/hash';
 import DOMHelper from 'ember-htmlbars/system/dom-helper';
@@ -152,11 +150,6 @@ registerHelper('-join-classes', joinClassesHelper);
 registerHelper('-html-safe', htmlSafeHelper);
 registerHelper('hash', hashHelper);
 
-if (Ember.ENV._ENABLE_LEGACY_VIEW_SUPPORT) {
-  registerHelper('-legacy-each-with-controller', legacyEachWithControllerHelper);
-  registerHelper('-legacy-each-with-keyword', legacyEachWithKeywordHelper);
-}
-
 Ember.HTMLBars = {
   template: template,
   compile: compile,