Change the timing to emit 'msg' event to consume a buffer in advance

[shinichy]

When I work with msgpack.Stream + deasync(https://github.com/abbr/deasync), the following program causes stack overflow.
This issue is caused because msgpack.Stream emits 'msg' event before it consumes a buffer and deasync allows processing io events before finishing 'msg' event callbacks.
I know this doesn't usually happen but it's better to emit 'msg' after consuming a buffer to handle this kind of case.

'use strict'

var net = require('net');
var path = '/tmp/deasync.sock';
var msgpack = require('msgpack');

var server = net.createServer(function(c) {
  c.on('data', function() {
    c.write(msgpack.pack('foo'));
  });
  c.on('end', function() {
    console.log('end')
    server.close()
  })
  c.write(msgpack.pack('hello'));
});
server.listen(path);

var done = false;
var client = net.createConnection(path)
var stream = new msgpack.Stream(client)
stream.on('msg', function(msg) {
  console.log('msg: ' + msg)
  if (msg === 'hello') {
    client.write(msgpack.pack('foo'));
    require('deasync').loopWhile(() => !done);
    console.log('done');
    client.end()
  } else if (msg === 'foo') {
    done = true;
  }
});

Output

msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
msg: hello
:0



RangeError: Maximum call stack size exceeded

[enochgroot]

Superseded by 2.0.0 (#25687, e04c9b5). Stream now consumes the frame before emitting 'msg' (lib/msgpack.js), which is the change this PR proposed.

[enochgroot]

Re-evaluated on master e04c9b55. Stream already snapshots bytes_remaining and consumes the frame before emit('msg').

Repro, Node v20.20.2:

• concatenated pack('a')+pack('b'), listener for 'a' called unpack([0x01]) → both frames delivered ["a","b"]
• throw in the listener → emit count 1, no replay

Covered by delivers both frames when a msg listener calls unpack and does not re-emit a frame whose msg listener threw. Closing this PR as superseded by 2.0.0.