feat: remove packet type when encoding binary packets

Only packets of 'message' type can contain binary data, so it makes sense to remove the prefix in
order to avoid the concatenation of the packet type.

Breaking change: the packet containing binary data will now be sent without any transformation

Protocol v3: { type: 'message', data: <Buffer 01 02 03> } => <Buffer 04 01 02 03>
Protocol v4: { type: 'message', data: <Buffer 01 02 03> } => <Buffer 01 02 03>