minor #3779 [Map] Render each UX icon once instead of once per marker (Kocal)

This PR was merged into the 3.x branch.

Discussion
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[Map] Render each UX icon once instead of once per marker

| Q              | A
| -------------- | ---
| Bug fix?       | no
| New feature?   | no
| Deprecations?  | no
| Documentation? | no
| Issues         | -
| License        | MIT

Markers on a map almost always share the same icon, but `AbstractRenderer::getMapAttributes()` called `UxIconRenderer::render()` for every single marker: a registry lookup, two attribute-validation passes and an HTML build, repeated identically thousands of times.

Memoize inside `UxIconRenderer` on the arguments it receives, so the cache key can't drift from them and every map in the request shares it. The generated payload is unchanged.

Rendering a Leaflet map: 1000 markers ~9.7 ms -> ~6.5 ms, 5000 markers ~53 ms -> ~37 ms.

Benchmarked from the repository root with `blackfire run symfony php bench.php`:

```php
<?php
require __DIR__.'/src/Map/vendor/autoload.php';
require __DIR__.'/src/Map/src/Bridge/Leaflet/vendor/autoload.php';

use Symfony\UX\Icons\Icon as UxIconsIcon;
use Symfony\UX\Icons\IconRegistryInterface;
use Symfony\UX\Icons\IconRenderer;
use Symfony\UX\Map\Bridge\Leaflet\Renderer\LeafletRenderer;
use Symfony\UX\Map\Icon\Icon;
use Symfony\UX\Map\Icon\UxIconRenderer;
use Symfony\UX\Map\Map;
use Symfony\UX\Map\Marker;
use Symfony\UX\Map\Point;
use Symfony\UX\StimulusBundle\Helper\StimulusHelper;

$registry = new class implements IconRegistryInterface {
    public function get(string $name): UxIconsIcon
    {
        return new UxIconsIcon(
            '<path d="M20 10c0 6-8 12-8 12s-8-6-8-12a8 8 0 0 1 16 0Z"/><circle cx="12" cy="10" r="3"/>',
            ['viewBox' => '0 0 24 24', 'fill' => 'none', 'stroke' => 'currentColor', 'stroke-width' => '2'],
        );
    }
};

$renderer = new LeafletRenderer(
    new StimulusHelper(null),
    new UxIconRenderer(new IconRenderer($registry, ['fill' => 'currentColor'])),
);

$map = new Map(center: new Point(48.86, 2.35), zoom: 12);
for ($i = 0; $i < 2000; ++$i) {
    $map->addMarker(new Marker(
        position: new Point(48.86 + $i / 10000, 2.35 + $i / 10000),
        title: 'Marker '.$i,
        icon: Icon::ux('lucide:map-pin'),
    ));
}

$renderer->renderMap($map);
```

Blackfire:

- before (177ms wall / 164ms CPU / 9MB): https://app.blackfire.io/envs/5f4f9a62-eaa0-45ee-b7b3-a1b879f550e9/profiles/e78d0d4c-5a78-4a30-a550-7ba075c36a90/graph
- after (82ms wall / 81ms CPU / 8MB): https://app.blackfire.io/envs/5f4f9a62-eaa0-45ee-b7b3-a1b879f550e9/profiles/b299a751-fac7-4e67-96bb-4d0dcb0dda8c/graph
- diff: https://app.blackfire.io/envs/5f4f9a62-eaa0-45ee-b7b3-a1b879f550e9/profiles/compare/e78d0d4c-5a78-4a30-a550-7ba075c36a90...b299a751-fac7-4e67-96bb-4d0dcb0dda8c/graph

Analysis, implementation and benchmarks by Claude Opus 5.

Commits
-------

3291457 [Map] Render each UX icon once instead of once per marker

Author: Kocal

src/Map/src/Icon/UxIconRenderer.php

@@ -20,6 +20,11 @@
  */
 class UxIconRenderer
 {
+    /**
+     * @var array<string, string>
+     */
+    private array $rendered = [];
+
     public function __construct(
         private readonly ?IconRendererInterface $renderer,
     ) {
@@ -34,7 +39,9 @@ public function render(string $name, array $attributes = []): string
             throw new \LogicException('You cannot use an UX Icon as the "UX Icons" package is not installed. Try running "composer require symfony/ux-icons" to install it.');
         }
 
-        return $this->renderer->renderIcon($name, [
+        // Markers of a map overwhelmingly share the same icon, so the same SVG
+        // was rebuilt once per marker.
+        return $this->rendered[$name.'|'.serialize($attributes)] ??= $this->renderer->renderIcon($name, [
             'xmlns' => 'http://www.w3.org/2000/svg',
             ...$attributes,
         ]);