Add no_std test example and update alloc gating

Update codegen to make `bytes` imports conditional on the `alloc`
feature and add a test example for the `thumbv7em-none-eabihf`
target.

roto-tonic/Cargo.toml

@@ -12,6 +12,7 @@ http-body = "1.0"
 http-body-util = "0.1"
 tower = "0.4"
 futures-util = "0.3"
+async-trait = "0.1"
 tokio-stream = { version = "0.1", features = ["net"] }
 tokio = { version = "1.38", features = ["full"] }
 http = "1.1"

roto-tonic/src/generated/interop.rs

@@ -5,18 +5,16 @@ use roto_runtime::{ProtoAccessor, ProtoBuilder, Result, RotoError, read_varint,
 use std::str;
 use bytes::{Bytes, BytesMut, Buf, BufMut};
 use tonic::{Request, Response, Status};
-use tokio_stream::Stream;
-use std::pin::Pin;
 use std::sync::Arc;
+use std::pin::Pin;
 use std::task::{Context, Poll};
 use std::future::Future;
-use tonic::body::BoxBody;
 use tower::Service;
-use futures_util::StreamExt;
-use http_body_util::BodyExt;
-use http_body::Body;
+use tonic::body::BoxBody;
+use tokio_stream::Stream;
 use crate::{BufferPool, StatusBody};
-
+use async_trait::async_trait;
+use http_body_util::BodyExt;
 
 pub struct UnaryRequest<'a> {
     accessor: roto_runtime::ProtoAccessor<'a>,
@@ -406,7 +404,8 @@ impl roto_runtime::RotoMessage for OwnedStreamingResponse {
     }
 }
 
-#[tonic::async_trait]
+
+#[async_trait]
 pub trait InteropService: Send + Sync + 'static {
     async fn unary_call(&self, request: Request<OwnedUnaryRequest>) -> std::result::Result<Response<OwnedUnaryResponse>, Status>;
     async fn streaming_call(&self, request: Request<OwnedStreamingRequest>) -> std::result::Result<Response<Pin<Box<dyn Stream<Item = std::result::Result<OwnedStreamingResponse, Status>> + Send>>>, Status>;