minor #36193 [DI] dump factory files as classes (nicolas-grekas)

This PR was merged into the 5.1-dev branch.

Discussion
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[DI] dump factory files as classes

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

This PR is a performance improvement when using `bin/console` on the command line.

Once upon a time, we advised setting `container.dumper.inline_factories` to `false` so that the container could be chunked into many files. More recently, we turned this setting back to `true` in order to optimize for preloading. But this made `bin/console` back to slow: since the CLI cannot have opcache, PHP has to parse this potentially big file all the time. Previous data already showed this can grow big.

This PR fixes the issue by generating many files again. But instead of generating the inline code within each file, we now wrap this code inside a class. Then we list this class for preloading.

This way, we have the best of both worlds: a `bin/console` that scales no matter the size of the app and top perf when using preloading (I benched a small hello world before/after the patch with preloading enabled, there is no measurable difference.)

This should also fix a memory leak that happens when factory files contain closures.

Commits
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cedb5cd429 [DI] dump factory files as classes

Author: nicolas-grekas

Kernel/MicroKernelTrait.php

@@ -142,6 +142,10 @@ public function registerContainerConfiguration(LoaderInterface $loader)
             }
 
             $container->setAlias(static::class, 'kernel')->setPublic(true);
+
+            if (!$container->hasParameter('container.dumper.inline_factories')) {
+                $container->setParameter('container.dumper.inline_factories', false);
+            }
         });
     }