Implement stream::cycle(..)

[felipesere]

This is a rough initial step that is able to take a vec and cycle it indefinitly.

I saw there were comments on #34 about the API and using IntoStream.
Would I have to impl IntoStream for a Vec<T> myself to be able to have the example be liek below?

use stream::IntoStream;

let vals = vec![1,2,3];
let s = vals.into_stream().cycle();

assert_eq!(s.next().await, Some(1));
assert_eq!(s.next().await, Some(2));
assert_eq!(s.next().await, Some(3));
assert_eq!(s.next().await, Some(1));
assert_eq!(s.next().await, Some(2));

I'm happy to get some pointers and see this through :)

Ref: #129

[k-nasa]

I'm sorry if it is an extra opinion.

[yoshuawuyts]

Thanks so much for this patch! -- @k-nasa's feedback is on point, and some of the API would need to change before we can merge this. This is heading in the right direction though, and thanks so much for working on this!

[felipesere]

@yoshuawuyts The bounds are adjusted and we take as Stream as argument.

What API changes do you have in mind? Should I attach it to stream itself so once can write

let s = stream::once(7).cycle();

[yoshuawuyts]

@felipesere yes, that's exactly what I was hoping you'd say! -- this should indeed be a method on Stream. Very excited for progress on this; we're getting real close to having all methods on Stream implemented!

[felipesere]

@yoshuawuyts I've moved it, but I think clippy is unhappy on CI and not in a mood to run? 😃

[felipesere]

@k-nasa @yoshuawuyts anything else to add? 😅

[felipesere]

@yoshuawuyts anything I should still do on this? :)

[yoshuawuyts]

This looks great, thank you!