message: transport/packet: Be more verbose in some variable names
  Prefer naming of tuple params for readability over by position index.
  Name a local variable for version more verbosely.
  Avoid some "as" casts with into().
diff: @@ -225,12 +225,12 @@ pub fn decode_packet_hdr(dec: &PacketDecoder, pd: &[u8]) -> Res<PacketHdr> {
  return Ok(p);
  }
  - let v = d.decode_uint(4)? as u32;
  - let idl = decode_cidl(d.decode_byte()?);
  + let version = d.decode_uint(4)? as u32;
  + let (dest_len, src_len) = decode_cidl(d.decode_byte()?);
  - p.dcid = ConnectionId(d.decode_data(idl.0 as usize)?);
  - p.scid = Some(ConnectionId(d.decode_data(idl.1 as usize)?));
  - if v == 0 {
  + p.dcid = ConnectionId(d.decode_data(dest_len.into())?);
  + p.scid = Some(ConnectionId(d.decode_data(src_len.into())?));
  + if version == 0 {
  let mut vns = vec![];
  while d.remaining() > 0 {
  