Feture: Reduce memory allocation during the Encode process to improve encoding performance.

[ethan256]

The current encoding process generates a large amount of memory allocation, and the GC pressure will increase when the QPS becomes large. Consider reducing the number of memory allocations to optimize the encoding process.

Here is my proposal:

1. Modify the BinaryEncoder interface definition

type BinaryEncoder interface {
	Encode(s *Stream)
}

Reduce NewBuffer calls by stitching each field encoding result directly through Stream. the Stream definition is as follows:

type Stream struct {
	buf []byte
	byte []byte
	err error
}

Stream implements the WriteXxx method from the original Buffer.

2. The Encode methods of all types that implement the BinaryEncoder interface require only minor modifications, such as DataValue:

func (d *DataValue) Encode(s *Stream) {
	s.WriteUint8(d.EncodingMask)

	if d.Has(DataValueValue) {
		s.WriteAny(d.Value)
	}
	if d.Has(DataValueStatusCode) {
		s.WriteUint32(uint32(d.Status))
	}
	if d.Has(DataValueSourceTimestamp) {
		s.WriteTime(d.SourceTimestamp)
	}
	if d.Has(DataValueSourcePicoseconds) {
		s.WriteUint16(d.SourcePicoseconds)
	}
	if d.Has(DataValueServerTimestamp) {
		s.WriteTime(d.ServerTimestamp)
	}
	if d.Has(DataValueServerPicoseconds) {
		s.WriteUint16(d.ServerPicoseconds)
	}
}

For detailed implementation, please refer to #726