bug #17926 [DependencyInjection] Enable alias for service_container (hason)

This PR was merged into the 2.3 branch.

Discussion
----------

[DependencyInjection] Enable alias for service_container

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Commits
-------

6161438 [DependencyInjection] Enabled alias for service_container

Author: fabpot

Compiler/ReplaceAliasByActualDefinitionPass.php

@@ -42,6 +42,10 @@ public function process(ContainerBuilder $container)
         foreach ($container->getAliases() as $id => $alias) {
             $aliasId = (string) $alias;
 
+            if ('service_container' === $aliasId) {
+                continue;
+            }
+
             try {
                 $definition = $container->getDefinition($aliasId);
             } catch (InvalidArgumentException $e) {

Tests/Compiler/ReplaceAliasByActualDefinitionPassTest.php

@@ -34,6 +34,8 @@ public function testProcess()
         $container->setAlias('a_alias', 'a');
         $container->setAlias('b_alias', 'b');
 
+        $container->setAlias('container', 'service_container');
+
         $this->process($container);
 
         $this->assertTrue($container->has('a'), '->process() does nothing to public definitions.');
@@ -44,6 +46,7 @@ public function testProcess()
             '->process() replaces alias to actual.'
         );
         $this->assertSame('b_alias', $aDefinition->getFactoryService());
+        $this->assertTrue($container->has('container'));
     }
 
     /**