[php-src] PR #24144: test: run-test.php stdout/stderr selection

Pull Request: https://github.com/php/php-src/pull/24144 Author: morrisonlevi Targeting PHP 8.4 instead of master because there can be timeouts without the fix, which wastes a lot of time. This fixes a problem when we're capturing both stderr and stdout and there isn't any stdout to be captured anymore, but we have stderr left to read. The loop would previously continue to fread on the stdout stream and not read from stderr. If the test has enough pending stderr data being written, then the kernel buffer can fill up and then block the writer until someone reads it. But if the reader is supposed to be run-tests.php then it wasn't ever being read.