Co-authored-by: luka <luyuyang@xiaohongshu.com>

This implements a custom `Debug` impl for `Stream` so that the `Waker`
type stored in the `*_task` fields does not get printed. This is because
the `Debug` impl of `Waker` prints a pointer which is non-deterministic.
My use-case here is that I am trying to make turmoil deterministic and
testing it with h2 via comparing trace logs between two same seeded
runs.