Made `debug:container` and `debug:autowiring` ignore starting backslash in service id

src/Symfony/Bundle/FrameworkBundle/Command/ContainerDebugCommand.php

@@ -220,6 +220,8 @@ EOF
 
     private function findProperServiceName(InputInterface $input, SymfonyStyle $io, ContainerBuilder $builder, string $name, bool $showHidden)
     {
+        $name = ltrim($name, '\\');
+
         if ($builder->has($name) || !$input->isInteractive()) {
             return $name;
         }

src/Symfony/Bundle/FrameworkBundle/Tests/Functional/ContainerDebugCommandTest.php

@@ -85,6 +85,7 @@ class ContainerDebugCommandTest extends WebTestCase
         return [
             [BackslashClass::class],
             ['FixturesBackslashClass'],
+            ['\\'.BackslashClass::class],
         ];
     }
 }