Go SDK: Add unit tests for command serialization/deserialization

## Description
The Go SDK contains numerous command types that implement the `MarshalBinary` interface to handle binary serialization. Currently, many of these implementations lack comprehensive unit tests, which is essential for ensuring data integrity and protocol compatibility.

## Task
Add unit tests to verify the correctness of the `MarshalBinary` implementations for all command types. The tests should ensure that the serialized output matches the expected binary format used by the Iggy server.

Go Command Types: [foreign/go/internal/command](https://github.com/apache/iggy/tree/master/foreign/go/internal/command). You should write tests for them.

Start in foreign/go/internal/command and inventory the command types that implement MarshalBinary. Read the existing serialization code and identify the expected binary format for each command, then add unit tests covering all command types and verify their serialized output matches the Iggy server protocol.

Written by the indexing model from the issue text.