The additional access rule checks for PHP-FPM added by #18398 do not respect the
config.ini.php setting and are therefore causing unwanted http requests for config files when the setting is set to disabled.
This PR adjusts this diagnostic check to only attempt file access if the config setting allows it.
I've simplified it so that the file access warning message will only be shown if they are using PHP-FPM and the
enable_required_directories_diagnostic is not disabled and the file is accessible, for all other scenarios it will just show the sapi name. Also switched to using the