Detect unintentional multiple `*.config.php` files to catch weird config problems

Detect unintentional multiple *.config.php files to catch weird config problems : Sometimes an administrator makes a manual backup of their existing config before making an adjustment. If they name it {anything}.config.php this results in them unintentionally having overlapping config files. And it also means the backup takes precedence. This creates all sorts of unexpected behaviors that can be difficult to isolate (and may give the appearance of bugs)[^exhibitA].