Remove async-trait crate as dependency for traces (#2339)

Author: lalitb

opentelemetry-sdk/Cargo.toml

@@ -43,7 +43,7 @@ pprof = { version = "0.13", features = ["flamegraph", "criterion"] }
 
 [features]
 default = ["trace", "metrics", "logs", "internal-logs"]
-trace = ["opentelemetry/trace", "rand", "async-trait", "percent-encoding"]
+trace = ["opentelemetry/trace", "rand", "percent-encoding"]
 jaeger_remote_sampler = ["trace", "opentelemetry-http", "http", "serde", "serde_json", "url"]
 logs = ["opentelemetry/logs", "async-trait", "serde_json"]
 spec_unstable_logs_enabled = ["logs", "opentelemetry/spec_unstable_logs_enabled"]

opentelemetry-sdk/src/trace/span_processor.rs

@@ -727,7 +727,6 @@ mod tests {
         OTEL_BSP_MAX_CONCURRENT_EXPORTS_DEFAULT, OTEL_BSP_MAX_EXPORT_BATCH_SIZE_DEFAULT,
     };
     use crate::trace::{BatchConfig, BatchConfigBuilder, SpanEvents, SpanLinks};
-    use async_trait::async_trait;
     use opentelemetry::trace::{SpanContext, SpanId, SpanKind, Status};
     use std::fmt::Debug;
     use std::future::Future;
@@ -963,7 +962,6 @@ mod tests {
         }
     }
 
-    #[async_trait]
     impl<D, DS> SpanExporter for BlockingExporter<D>
     where
         D: Fn(Duration) -> DS + 'static + Send + Sync,