refactor(lib): Import tracing macros per-module

Instead of one #[macro_use] at the crate root.

src/upgrade.rs

@@ -14,6 +14,8 @@ use std::marker::Unpin;
 use bytes::Bytes;
 use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
 use tokio::sync::oneshot;
+#[cfg(any(feature = "http1", feature = "http2"))]
+use tracing::trace;
 
 use crate::common::io::Rewind;
 use crate::common::{task, Future, Pin, Poll};