[php-src] Issue #15274: stop a child when used more than x mb ram after stop process

Issue: https://github.com/php/php-src/issues/15274 Author: parsibox ### Description hi we have a problem in https://github.com/PHPOffice/PHPExcel/ that not release memory after load excel and our child in php-fpm 7.4 use all of server ram we need to stop that child after process done and do not receive new request on that child after stop a child it release that memory so if we have an option of max used ram for a child in www.conf we can set it i see you have "last request memory" in status that can used for this feature