Add tokio-stream wrappers for watch and broadcast receivers

[peku33]

In tokio 0.2 watch and broadcast receivers implemented Stream.
In tokio 1.0 they don't.

While I know watch and broadcast will probably never be Stream themselves, there is some work in progress to make them convertible into Streams: #3303

While this is still in progress - is it possible to have watch and broadcast receiver wrappers added to tokio-stream?

[Darksonn]

We can add wrappers that just internally use the async-stream crate. We can't do better as the channels have no poll_recv method.

[peku33]

Yes, please

[liufuyang]

I will give a try to see if I can help adding it :)

[jhpratt]

This would be wonderful to have! It's the only thing preventing me from doing a full upgrade to tokio 1.0 on a major project of mine.

[liufuyang]

Sorry I got dragged away for something else and couldn't find time finishing it up. Perhaps I can take a look at it this coming weekends. Otherwise @Darksonn might be able to give me a hand or just do this on her own if I am too slow progressing :)

[peku33]

Hi, any update on this?

[Darksonn]

Yes! The wrappers were waiting for #3464, which was just released in tokio-util v0.3.6 one hour ago.

[Darksonn]

The wrappers are out in tokio-stream v0.1.3.