fix(Instrumentation/Cache): add iterable value type for $metadata parameter

Satisfies PHPStan's missingType.iterableValue rule on the get() methods of
TraceableCacheAdapter and TagAwareTraceableCacheAdapter while staying
contravariant with Symfony's CacheInterface::get() signature.

Author: gaelreyrol

src/Instrumentation/Symfony/Cache/TagAwareTraceableCacheAdapter.php

@@ -25,6 +25,9 @@ public function __construct(
         $this->logger = $logger;
     }
 
+    /**
+     * @param array<array-key, mixed>|null $metadata
+     */
     public function get(string $key, callable $callback, ?float $beta = null, ?array &$metadata = null): mixed
     {
         return $this->tracer->traceFunction(

src/Instrumentation/Symfony/Cache/TraceableCacheAdapter.php

@@ -24,6 +24,9 @@ public function __construct(
         $this->logger = $logger;
     }
 
+    /**
+     * @param array<array-key, mixed>|null $metadata
+     */
     public function get(string $key, callable $callback, ?float $beta = null, ?array &$metadata = null): mixed
     {
         return $this->tracer->traceFunction(