Add condition option on legacy routing (#1048)

| Q               | A
| --------------- | -----
| Bug fix?        | no
| New feature?    | yes
| BC breaks?      | no
| Deprecations?   | no
| Related tickets |
| License         | MIT

To create a bc-layer for the legacy routes in Sylius E-commerce project,
I need to add some route conditions to existing routes.

On simple route, I'm able to create this condition:
```yaml
sylius_admin_product_create_simple:
    path: /products/new/simple
    methods: [GET, POST]
    condition: "context.isSyliusRoutingBcLayerEnabled() || context.isSyliusRoutingBcLayerEnabled('admin_product')"
    # ...
```

But I also need to add this condition on multiple routing definition
like this following one and that's the reason of this PR.

```yaml
sylius_admin_product:
    resource: |
        alias: sylius.product
        condition: "context.isSyliusRoutingBcLayerEnabled() || context.isSyliusRoutingBcLayerEnabled('admin_product')"
        # ...
    type: sylius.resource
```

To bring more context, here is the RequestContext we will implement on
Sylius core to create the bc-layer
```php
namespace Sylius\Bundle\CoreBundle\Routing;

use Symfony\Component\Routing\RequestContext as BaseRequestContext;

final class RequestContext extends BaseRequestContext
{
    public function __construct(
        BaseRequestContext $decorated,
        private array $bcLayerConfig,
    ) {
        // ...
    }

    public function isSyliusRoutingBcLayerEnabled(?string $key = null): bool
    {
        if (null === $key) {
            return $this->bcLayerConfig['enabled'] ?? false;
        }

        return $this->bcLayerConfig['routes'][$key]['enabled'] ?? false;
    }
}
```

Author: NoResponseMate

src/Bundle/Routing/Configuration.php

@@ -43,6 +43,7 @@ public function getConfigTreeBuilder(): TreeBuilder
                 ->scalarNode('templates')->cannotBeEmpty()->end()
                 ->scalarNode('grid')->cannotBeEmpty()->end()
                 ->booleanNode('permission')->defaultValue(false)->end()
+                ->scalarNode('condition')->cannotBeEmpty()->end()
                 ->arrayNode('except')
                     ->scalarPrototype()->end()
                 ->end()

src/Bundle/Routing/ResourceLoader.php

@@ -179,7 +179,9 @@ private function createRoute(
             ];
         }
 
-        return $this->routeFactory->createRoute($path, $defaults, [], [], '', [], $methods);
+        $condition = $configuration['condition'] ?? '';
+
+        return $this->routeFactory->createRoute($path, $defaults, [], [], '', [], $methods, $condition);
     }
 
     private function getRouteName(MetadataInterface $metadata, array $configuration, string $actionName): string