fix: reject Close packets with unexpected payloads

[immanuwell]

Description

Tighten Close decoding a bit. Right now Vortex::try_from accepts Close packets with extra bytes, which is kinda wonky because Close is documented and serialized as zero length.

Related Issue

Closes #104

Motivation and Context

This is easy to trigger in practice. The malformed packet is only 10 bytes total, so no quota or hard limit gets in the way. Any buggy peer can send it.

Repro on main:

use bytes::{Bytes, BytesMut};
use vortex_protocol::{Header, Vortex};
use vortex_protocol::tlv::Tag;

let header = Header::new(Tag::Close, 4);
let header_bytes: Bytes = header.into();
let value = Bytes::from_static(b"test");

let mut packet_bytes = BytesMut::new();
packet_bytes.extend_from_slice(&header_bytes);
packet_bytes.extend_from_slice(&value);

let packet = Vortex::try_from(packet_bytes.freeze());

Before this patch it parses as Vortex::Close(_) and drops the payload on re encode. After this patch it returns InvalidLength. tiny fix, but it keeps the codec honest.

Screenshots (if appropriate)

n/a