[php-src] Issue #10024: support linting multiple files at once using `php -l`

Issue: https://github.com/php/php-src/issues/10024 Author: staabm ### Description would it be possible to support passing multiple files to php -l, e.g. php -l file1.php file2.php file3.php? my request is motivated by the fact the current linting tools are slow because of the overhead involved to lint every single file using a single process, so e.g. proc_open dominates the whole process. see this example blackfire profile, where I lint a project with 2890 files which takes 1min 14secs:  if we could e.g. lint 2 or 3 files at a time we could easily cut this processing time in half.