ENGCOM-7484: #27962 Migrate Plugin out of Framework (to Theme module) #27965

 - Merge Pull Request #27965 from lbajsarowicz/magento2:bugfix/move-plugin
 - Merged commits:
   1. d938e7b
   2. ae58f56
   3. 02aae13
   4. a84633e
   5. 7ff6063

Author: magento-engcom-team

app/code/Magento/Store/etc/di.xml

@@ -65,7 +65,6 @@
     <preference for="Magento\Framework\App\Router\PathConfigInterface" type="Magento\Store\Model\PathConfig" />
     <type name="Magento\Framework\App\ActionInterface">
         <plugin name="storeCheck" type="Magento\Store\App\Action\Plugin\StoreCheck"/>
-        <plugin name="designLoader" type="Magento\Framework\App\Action\Plugin\LoadDesignPlugin"/>
         <plugin name="eventDispatch"  type="Magento\Framework\App\Action\Plugin\EventDispatchPlugin"/>
         <plugin name="actionFlagNoDispatch"  type="Magento\Framework\App\Action\Plugin\ActionFlagNoDispatchPlugin"/>
     </type>

lib/internal/Magento/Framework/App/Action/Plugin/LoadDesignPlugin.php renamed to app/code/Magento/Theme/Plugin/LoadDesignPlugin.php

@@ -4,7 +4,7 @@
  * See COPYING.txt for license details.
  */
 
-namespace Magento\Framework\App\Action\Plugin;
+namespace Magento\Theme\Plugin;
 
 use Magento\Framework\App\ActionInterface;
 use Magento\Framework\Config\Dom\ValidationException;
@@ -21,12 +21,12 @@ class LoadDesignPlugin
     /**
      * @var DesignLoader
      */
-    protected $_designLoader;
+    private $designLoader;
 
     /**
      * @var MessageManagerInterface
      */
-    protected $messageManager;
+    private $messageManager;
 
     /**
      * @param DesignLoader $designLoader
@@ -36,7 +36,7 @@ public function __construct(
         DesignLoader $designLoader,
         MessageManagerInterface $messageManager
     ) {
-        $this->_designLoader = $designLoader;
+        $this->designLoader = $designLoader;
         $this->messageManager = $messageManager;
     }
 
@@ -50,7 +50,7 @@ public function __construct(
     public function beforeExecute(ActionInterface $subject)
     {
         try {
-            $this->_designLoader->load();
+            $this->designLoader->load();
         } catch (LocalizedException $e) {
             if ($e->getPrevious() instanceof ValidationException) {
                 /** @var MessageInterface $message */

lib/internal/Magento/Framework/App/Test/Unit/Action/Plugin/LoadDesignPluginTest.php renamed to app/code/Magento/Theme/Test/Unit/Plugin/LoadDesignPluginTest.php

@@ -3,15 +3,13 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
-declare(strict_types=1);
-
-namespace Magento\Framework\App\Test\Unit\Action\Plugin;
+namespace Magento\Theme\Test\Unit\Plugin;
 
 use Magento\Framework\App\Action\Action;
-use Magento\Framework\App\Action\Plugin\LoadDesignPlugin;
 use Magento\Framework\App\ActionInterface;
 use Magento\Framework\Message\ManagerInterface;
 use Magento\Framework\View\DesignLoader;
+use Magento\Theme\Plugin\LoadDesignPlugin;
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 
@@ -26,7 +24,7 @@ public function testBeforeExecute()
         $designLoaderMock = $this->createMock(DesignLoader::class);
 
         /** @var MockObject|ManagerInterface $messageManagerMock */
-        $messageManagerMock = $this->getMockForAbstractClass(ManagerInterface::class);
+        $messageManagerMock = $this->createMock(ManagerInterface::class);
 
         $plugin = new LoadDesignPlugin($designLoaderMock, $messageManagerMock);
 

app/code/Magento/Theme/etc/di.xml

@@ -105,6 +105,9 @@
             <argument name="scope" xsi:type="const">Magento\Store\Model\ScopeInterface::SCOPE_STORE</argument>
         </arguments>
     </virtualType>
+    <type name="Magento\Framework\App\ActionInterface">
+        <plugin name="designLoader" type="Magento\Theme\Plugin\LoadDesignPlugin"/>
+    </type>
     <type name="Magento\Framework\View\Element\UiComponent\DataProvider\CollectionFactory">
         <arguments>
              <argument name="collections" xsi:type="array">