test: isolate CorsTest to prevent global state pollution

Author: gr8man

tests/system/HTTP/CorsTest.php

@@ -14,14 +14,22 @@
 namespace CodeIgniter\HTTP;
 
 use CodeIgniter\Test\CIUnitTestCase;
+use PHPUnit\Framework\Attributes\BackupGlobals;
 use PHPUnit\Framework\Attributes\Group;
 
 /**
  * @internal
  */
+#[BackupGlobals(true)]
 #[Group('Others')]
 final class CorsTest extends CIUnitTestCase
 {
+    protected function setUp(): void
+    {
+        $this->resetServices();
+        parent::setUp();
+    }
+
     /**
      * @param array{
      *      allowedOrigins?: list<string>,