Using FnStream in place of a stream! macro from the async-stream crate

[ysaito1001]

Related to #2910, this page shows a snippet how a stream! macro from the async-stream crate can be upgraded by using aws_smithy_async::future::fn_stream::FnStream.

Before

use async_stream::stream;
use aws_sdk_transcribestreaming::Client;
use aws_sdk_transcribestreaming::primitives::Blob;
use aws_sdk_transcribestreaming::types::{AudioEvent, AudioStream};

const CHUNK_SIZE: usize = 8192;

fn pcm_data() -> Vec<u8> {
    // --snip--
}

fn main() {
    let input_stream = stream! {
        let pcm = pcm_data();
        for chunk in pcm.chunks(CHUNK_SIZE) {
            yield Ok(AudioStream::AudioEvent(AudioEvent::builder().audio_chunk(Blob::new(chunk)).build()));
        }
    };

    let sdk_config = aws_config::from_env().load().await;
    let client = Client::new(&sdk_config);
    client
        .start_stream_transcription()
        .audio_stream(input_stream.into())
        .send()
        .await
        .unwrap();
}

After (only differs in how the variable input_stream is initialized)

use aws_sdk_transcribestreaming::Client;
use aws_sdk_transcribestreaming::primitives::Blob;
use aws_sdk_transcribestreaming::types::{AudioEvent, AudioStream};
use aws_smithy_async::future::fn_stream::FnStream;

const CHUNK_SIZE: usize = 8192;

fn pcm_data() -> Vec<u8> {
    // --snip--
}

fn main() {
    let input_stream = FnStream::new(|tx| {
        Box::pin(async move {
            let pcm = pcm_data();
            for chunk in pcm.chunks(CHUNK_SIZE) {
                tx.send(Ok(AudioStream::AudioEvent(
                    AudioEvent::builder().audio_chunk(Blob::new(chunk)).build(),
                )))
                .await
                .expect("send should succeed");
            }
        })
    });

    let sdk_config = aws_config::from_env().load().await;
    let client = Client::new(&sdk_config);
    client
        .start_stream_transcription()
        .audio_stream(input_stream.into())
        .send()
        .await
        .unwrap();
}

[ysaito1001]

Closing this since #2910 itself was closed. We're not going to remove the Stream trait from event stream's public API.