StreamExt: add chunks and try_chunks

[SaltyKitkat]

I love this crate a lot because of its wonderful api and elegant implement. I really need chunks and try_chunks method for StreamExt, which is missing in this crate. So I forked this repo, and added them. And I wonder if this could be merged.

The codes are mainly from futures-rs with some changes:

1. Remove Sink and FusedStream related things
2. Remove references to TryStream
3. Rename type parameter St to S
4. fix size_hints as mentioned here
5. rewrite some inline docs to fit futures-lite and changes above

Thanks a lot for your reviewing this :)

[SaltyKitkat]

usize::div_ceil is stable since 1.73, while rustc in CI/msrv is 1.60 :(

[notgull]

I don't think this is the right API to expose in futures-lite, as it seems somewhat opinionated and allocation-heavy. Maybe an array_chunks-type API would be better, but that probably can't be done safely at the current MSRV.

So I don't think we should have this API. Thanks anyways!