Add YANET Functional Testing Framework

Overview

This PR introduces a functional testing framework for YANET using QEMU virtual machines. The framework enables end-to-end testing of dataplane and controlplane modules in isolated environments.

Key Features

QEMU-based Testing

• Isolated VM per test using Ubuntu 24.04 cloud image
• Autologin via serial console
• Cross-platform support (Linux/macOS)

Network Architecture

• Unix domain sockets for packet transmission
• Real network environment testing
• Multiple network interface support

Integration

• 9P filesystem sharing for build artifacts
• VM executes real YANET processes from compiled binaries

Added Tests

• Framework Test: Basic infrastructure validation
• NAT64 Test: IPv4/IPv6 packet translation testing
• Decap Test: IPIP6 tunnel decapsulation validation

Implementation

• Thread-safe CLI command execution through serial console
• Packet injection and capture via socket connections
• Automatic VM lifecycle management with cleanup
• Added test-functional target to build system

The framework provides reliable functional testing in real network environments with complete test isolation and easy extensibility for additional modules.