feature symfony#61497 [ObjectMapper] cache attributes in memory (soyuka)

This PR was submitted for the 7.3 branch but it was squashed and merged into the 7.4 branch instead.

Discussion
----------

[ObjectMapper] cache attributes in memory

| Q             | A
| ------------- | ---
| Branch?       | 7.3
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | na
| License       | MIT

Profile:

<img width="1254" height="262" alt="20250821_22h15m27s_grim" src="https://github.com/user-attachments/assets/bf88422e-e01d-4768-aa1c-fdaa4dc87c38" />
<img width="1263" height="309" alt="20250821_22h15m12s_grim" src="https://github.com/user-attachments/assets/cd50f59d-7302-4cc0-8a25-2659922e0e89" />

<details>
<summary>phpbench</summary>
```php
<?php

namespace Symfony\Component\ObjectMapper\Benchmarks;

use PhpBench\Attributes as Bench;
use Symfony\Component\ObjectMapper\ObjectMapper;
use Symfony\Component\ObjectMapper\Tests\Fixtures\A;
use Symfony\Component\ObjectMapper\Tests\Fixtures\C;
use Symfony\Component\ObjectMapper\Tests\Fixtures\D;

#[Bench\BeforeMethods('setUp')]
class ObjectMapperBench
{
    private ObjectMapper $objectMapper;
    private A $sourceObject;

    public function setUp(): void
    {
        $this->objectMapper = new ObjectMapper();

        $d = new D(baz: 'foo', bat: 'bar');
        $c = new C(foo: 'foo', bar: 'bar');
        $this->sourceObject = new A();
        $this->sourceObject->foo = 'test';
        $this->sourceObject->transform = 'test';
        $this->sourceObject->baz = 'me';
        $this->sourceObject->notinb = 'test';
        $this->sourceObject->relation = $c;
        $this->sourceObject->relationNotMapped = $d;
    }

    #[Bench\Revs(100)]
    #[Bench\Iterations(5)]
    public function benchObjectMapper(): void
    {
        $this->objectMapper->map($this->sourceObject);
    }
}
```
</details>

Commits
-------

3576a57 [ObjectMapper] cache attributes in memory

Author: fabpot

src/Symfony/Component/ObjectMapper/Metadata/ReflectionObjectMapperMetadataFactory.php

@@ -21,17 +21,27 @@
  */
 final class ReflectionObjectMapperMetadataFactory implements ObjectMapperMetadataFactoryInterface
 {
+    private array $reflectionClassCache = [];
+    private array $attributesCache = [];
+
     public function create(object $object, ?string $property = null, array $context = []): array
     {
         try {
-            $refl = new \ReflectionClass($object);
-            $mapTo = [];
-            foreach (($property ? $refl->getProperty($property) : $refl)->getAttributes(Map::class, \ReflectionAttribute::IS_INSTANCEOF) as $mapAttribute) {
-                $map = $mapAttribute->newInstance();
-                $mapTo[] = new Mapping($map->target, $map->source, $map->if, $map->transform);
+            $key = $object::class.($property ?? '');
+
+            if (isset($this->attributesCache[$key])) {
+                return $this->attributesCache[$key];
+            }
+
+            $refl = $this->reflectionClassCache[$object::class] ??= new \ReflectionClass($object);
+            $attributes = ($property ? $refl->getProperty($property) : $refl)->getAttributes(Map::class, \ReflectionAttribute::IS_INSTANCEOF);
+            $mappings = [];
+            foreach ($attributes as $attribute) {
+                $map = $attribute->newInstance();
+                $mappings[] = new Mapping($map->target, $map->source, $map->if, $map->transform);
             }
 
-            return $mapTo;
+            return $this->attributesCache[$key] = $mappings;
         } catch (\ReflectionException $e) {
             throw new MappingException($e->getMessage(), $e->getCode(), $e);
         }