[FEATURE modernized-built-in-components] Extract shared code

Refactor to extra shared code into internal component to pave way
for implementing <LinkTo> with the new infrastructure.

Part of #19270

packages/@ember/-internals/glimmer/index.ts

@@ -366,9 +366,10 @@ export { templateFactory as template, templateCacheCounters } from '@glimmer/opc
 export { default as RootTemplate } from './lib/templates/root';
 export { default as Checkbox } from './lib/components/checkbox';
 export { default as TextField } from './lib/components/text-field';
-export { default as TextArea } from './lib/components/textarea';
+export { default as TextArea } from './lib/components/-textarea';
 export { default as LinkComponent } from './lib/components/link-to';
-export { default as Input, TextareaComponent as Textarea } from './lib/components/input';
+export { default as Input } from './lib/components/input';
+export { default as Textarea } from './lib/components/textarea';
 export { default as Component } from './lib/component';
 export { default as Helper, helper } from './lib/helper';
 export { SafeString, escapeExpression, htmlSafe, isHTMLSafe } from './lib/utils/string';

packages/@ember/-internals/glimmer/lib/components/-textarea.ts

@@ -0,0 +1,103 @@
+/**
+@module @ember/component
+*/
+import { CoreObject } from '@ember/-internals/runtime';
+import { TextSupport } from '@ember/-internals/views';
+import { EMBER_MODERNIZED_BUILT_IN_COMPONENTS } from '@ember/canary-features';
+import { deprecate } from '@ember/debug';
+import Component from '../component';
+import layout from '../templates/empty';
+
+/**
+  The internal representation used for `Textarea` invocations.
+
+  @class TextArea
+  @extends Component
+  @see {Ember.Templates.components.Textarea}
+  @uses Ember.TextSupport
+  @public
+*/
+const TextArea = Component.extend(TextSupport, {
+  classNames: ['ember-text-area'],
+
+  layout,
+
+  tagName: 'textarea',
+  attributeBindings: [
+    'rows',
+    'cols',
+    'name',
+    'selectionEnd',
+    'selectionStart',
+    'autocomplete',
+    'wrap',
+    'lang',
+    'dir',
+    'value',
+  ],
+  rows: null,
+  cols: null,
+});
+
+TextArea.toString = () => '@ember/component/text-area';
+
+if (EMBER_MODERNIZED_BUILT_IN_COMPONENTS) {
+  Object.defineProperty(TextArea, '_wasReopened', {
+    configurable: true,
+    enumerable: false,
+    writable: true,
+    value: false,
+  });
+
+  Object.defineProperty(TextArea, 'reopen', {
+    configurable: true,
+    enumerable: false,
+    writable: true,
+    value: function reopen(this: typeof TextArea, ...args: unknown[]): unknown {
+      if (this === TextArea) {
+        deprecate(
+          'Reopening Ember.TextArea is deprecated. Consider implementing your own ' +
+            'wrapper component or create a custom subclass.',
+          false,
+          {
+            id: 'ember.built-in-components.reopen',
+            for: 'ember-source',
+            since: {},
+            until: '4.0.0',
+          }
+        );
+
+        TextArea._wasReopened = true;
+      }
+
+      return CoreObject.reopen.call(this, ...args);
+    },
+  });
+
+  Object.defineProperty(TextArea, 'reopenClass', {
+    configurable: true,
+    enumerable: false,
+    writable: true,
+    value: function reopenClass(this: typeof TextArea, ...args: unknown[]): unknown {
+      if (this === TextArea) {
+        deprecate(
+          'Reopening Ember.TextArea is deprecated. Consider implementing your own ' +
+            'wrapper component or create a custom subclass.',
+          false,
+          {
+            id: 'ember.built-in-components.reopen',
+            for: 'ember-source',
+            since: {},
+            until: '4.0.0',
+          }
+        );
+
+        TextArea._wasReopened = true;
+      }
+
+      return CoreObject.reopenClass.call(this, ...args);
+    },
+  });
+}
+
+export default TextArea;