[php-src] PR #24782: Fix GH-24777: Free cached chunks before failing on memory_limit

Pull Request: https://github.com/php/php-src/pull/24782 Author: lazerg Chunks cached by zend_mm_shutdown() for the next request still count towards real_size. Small allocations reuse them, but a huge allocation is mapped separately, so after a few heavy requests a light request can hit memory_limit on its first huge allocation even though most of the counted memory is free. zend_mm_check_limit() now releases cached chunks when the limit would be exceeded after zend_mm_gc(), the same way zend_set_memory_limit() already does. Fixes #24777