… config (Nyholm)

This PR was merged into the 5.3-dev branch.

Discussion
----------

[DependencyInjection][Routing] Access environment in PHP config

| Q             | A
| ------------- | ---
| Branch?       | 5.x
| Bug fix?      | no
| New feature?  | yes
| Deprecations? |
| Tickets       |
| License       | MIT
| Doc PR        |

This will allow me to write config like:

```php
use Symfony\Config\FrameworkConfig;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;

return static function (FrameworkConfig $framework, ContainerConfigurator $container) {
    if ('test' === $container->env()) {
        $framework->test(true);
        $framework->session()->storageFactoryId('session.storage.mock_file');
    }
};
```

This PR will also revert parts of #40214. It is much simpler to maintain and write PHP config without `->when()`. Instead we add `ContainerConfigurator::env(): ?string` and `RoutingConfigurator::env(): ?string`.

```php

use App\Controller\BlogController;
use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

return function (RoutingConfigurator $routes) {
    if ($routes->env() === 'dev') {
        $routes->add('debug-stats', '/blog-debyg')
            ->controller([BlogController::class, 'debug'])
        ;
    }

    $routes->add('blog_list', '/blog')
        ->controller([BlogController::class, 'list'])
    ;
};
```

Commits
-------

11dfaa4 [DependencyInjection][Routing] Access environment in PHP config

…p autoregistering a class when the env doesn't match (nicolas-grekas)

This PR was merged into the 5.3-dev branch.

Discussion
----------

[DependencyInjection] Add `#[When(env: 'foo')]` to skip autoregistering a class when the env doesn't match

| Q             | A
| ------------- | ---
| Branch?       | 5.x
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

This is a follow up of #40214, in order to conditionally auto-register classes.

By adding a `#[When(env: prod)]` annotation on a class, one can tell that a class should be skipped when the current env doesn't match the one declared in the attribute.

This saves from writing similar conditional configuration by using the per-env `services_prod.yaml` convention (+corresponding exclusion from `services.yaml`), or some logic in the Kernel.

Commits
-------

59c75ba [DI] add `#[When(env: 'foo')]` to skip autoregistering a class when the env doesn't match