core/: Redesign upgrade::{write_one, write_with_len_prefix, read_one} (#2111)

1. Deprecating the `write_one` function

  Semantically, this function is a composition of `write_with_len_prefix` and
  `io.close()`. This represents a footgun because the `close` functionality is
  not obvious and only mentioned in the docs. Using this function multiple times
  on a single substream will produces hard to debug behaviour.

2. Deprecating `read_one` and `write_with_len_prefix` functions

3. Introducing `write_length_prefixed` and `read_length_prefixed`

- These functions are symmetric and do exactly what you would expect, just
  writing to the socket without closing
- They also have a symmetric interface (no more custom errors, just `io::Error`)

Co-authored-by: Max Inden <mail@max-inden.de>

protocols/identify/src/protocol.rs

@@ -186,7 +186,11 @@ where
 
     let mut bytes = Vec::with_capacity(message.encoded_len());
     message.encode(&mut bytes).expect("Vec<u8> provides capacity as needed");
-    upgrade::write_one(&mut io, &bytes).await
+
+    upgrade::write_length_prefixed(&mut io, bytes).await?;
+    io.close().await?;
+
+    Ok(())
 }
 
 async fn recv<T>(mut socket: T) -> io::Result<IdentifyInfo>
@@ -195,7 +199,7 @@ where
 {
     socket.close().await?;
 
-    let msg = upgrade::read_one(&mut socket, 4096)
+    let msg = upgrade::read_length_prefixed(&mut socket, 4096)
         .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
         .await?;