Previously, `into_raw_fd()` transferred fd ownership to epoll while
keeping separate clones in `reader` and `writer`, causing leaks when
the stream was closed. Now, `reader` owns the fd and epoll borrows it.
When the FD is closed in the kernel, reader will be reset to None.
Signed-off-by: Praveen K Paladugu <prapal@linux.microsoft.com>