[php-src] PR #23805: Map epoll_ctl() errors through php_poll_errno_to_error()

Pull Request: https://github.com/php/php-src/pull/23805 Author: nicolas-grekas The epoll backend reports everything but EEXIST and ENOENT as ERR_SYSTEM, so a caller cannot tell "this handle cannot be polled" from "polling is broken". The kqueue backend already maps errno through php_poll_errno_to_error(), this makes epoll do the same. EPERM gets its own case: epoll_ctl() returns it for files that do not implement polling, which means Context::add() fails for regular files, php://temp and /dev/null while Backend::Poll accepts them all: ``` Auto (epoll) Poll regular file FailedHandleAddException added ok /dev/null FailedHandleAddException added ok php://temp FailedHandleAddException added ok pipe added ok added ok socketpair added ok added ok ``` That is expected from epoll, and kqueue does not have the problem since it takes regular files. But an event loop has to deal with it, since STDIN is /dev/null in most CI runs and a plain file whenever it is redirected, and today the only way to detect the case is to try the handle again on a Backend::Poll context. With ERROR_NOSUPPORT it can fall back on the spot. /cc @bukka