refactor(http1): emit trace logs when buffering write data

src/proto/h1/io.rs

@@ -512,6 +512,11 @@ where
                 let head = self.headers_mut();
 
                 head.maybe_unshift(buf.remaining());
+                trace!(
+                    self.len = head.remaining(),
+                    buf.len = buf.remaining(),
+                    "buffer.flatten"
+                );
                 //perf: This is a little faster than <Vec as BufMut>>::put,
                 //but accomplishes the same result.
                 loop {
@@ -527,6 +532,11 @@ where
                 }
             }
             WriteStrategy::Queue => {
+                trace!(
+                    self.len = self.remaining(),
+                    buf.len = buf.remaining(),
+                    "buffer.queue"
+                );
                 self.queue.push(buf.into());
             }
         }