Merge branch '5.4' into 6.0

* 5.4:
  [Testing] use static::getContainer()
  Minor - Remove deprecated self::$container

Author: OskarStark

messenger.rst

@@ -1479,7 +1479,7 @@ during a request::
             $this->assertSame(200, $client->getResponse()->getStatusCode());
 
             /* @var InMemoryTransport $transport */
-            $transport = self::$container->get('messenger.transport.async_priority_normal');
+            $transport = $this->getContainer()->get('messenger.transport.async_priority_normal');
             $this->assertCount(1, $transport->getSent());
         }
     }

testing.rst

@@ -246,7 +246,7 @@ Retrieving Services in the Test
 
 In your integration tests, you often need to fetch the service from the
 service container to call a specific method. After booting the kernel,
-the container is stored in ``self::$container``::
+the container is stored in ``static::getContainer()``::
 
     // tests/Service/NewsletterGeneratorTest.php
     namespace App\Tests\Service;
@@ -261,8 +261,8 @@ the container is stored in ``self::$container``::
             // (1) boot the Symfony kernel
             self::bootKernel();
 
-            // (2) use self::$container to access the service container
-            $container = self::$container;
+            // (2) use static::getContainer() to access the service container
+            $container = static::getContainer();
 
             // (3) run some service & test the result
             $newsletterGenerator = $container->get(NewsletterGenerator::class);
@@ -272,7 +272,7 @@ the container is stored in ``self::$container``::
         }
     }
 
-The container in ``self::$container`` is actually a special test container.
+The container in ``static::getContainer()`` is actually a special test container.
 It gives you access to both the public services and the non-removed
 :ref:`private services <container-public>` services.