[php-src] PR #24169: Use-after-free when a user wrapper closes the other stream during stream_copy_to_stream()

Pull Request: https://github.com/php/php-src/pull/24169 Author: EdmondDantes _php_stream_copy_to_stream_ex() reads from src and writes to dest in a loop. When either is a user wrapper, its stream_write() or stream_read() may fclose() the other stream, and the next turn of the loop uses the freed stream (segfault, or an assertion in php_stream_memory_read() on a debug build). The fix sets PHP_STREAM_FLAG_NO_FCLOSE on both streams for the duration of the copy, the same protection a stream already gets while its user filter runs, so such an fclose() fails with the existing warning. Each stream's original flag is restored afterwards (both are read before either is set, so src == dest is fine). The body moved into a static helper so that none of its returns needed touching. Test: ext/standard/tests/streams/stream_copy_to_stream_close_in_callback.phpt, both directions. It segfaults without the fix. Known limit, left for a separate change: pclose(), proc_close() and closedir() free a stream without checking PHP_STREAM_FLAG_NO_FCLOSE (an opendir() handle can be the source of a copy).