fix(benchmarks): Ensure OPCache is used in cgi-fcgi web servers (#2538)

* fix(benchmarks): Ensure OPCache is used in cgi-fcgi web servers

* Use zend_extension=opcache.so instead

* Check if Zend OpCache is loaded

Co-authored-by: Bob Weinand <bob.weinand@datadoghq.com>

* Remove unused env var

---------

Co-authored-by: Bob Weinand <bob.weinand@datadoghq.com>

tests/Common/WebFrameworkTestCase.php

@@ -94,6 +94,8 @@ protected static function getEnvs()
      */
     protected static function getInis()
     {
+        $enableOpcache = \extension_loaded("Zend OpCache");
+
         return [
             'ddtrace.request_init_hook' => realpath(__DIR__ . '/../../bridge/dd_wrap_autoloader.php'),
             // The following values should be made configurable from the outside. I could not get env XDEBUG_CONFIG
@@ -102,7 +104,7 @@ protected static function getInis()
             'xdebug.remote_enable' => 1,
             'xdebug.remote_host' => 'host.docker.internal',
             'xdebug.remote_autostart' => 1,
-        ];
+        ] + ($enableOpcache ? ["zend_extension" => "opcache.so"] : []);
     }
 
     /**