Add cross-platform LocalTarget with macOS and Linux support

[denini08]

This PR introduces the new LocalTarget class, which unifies local target handling across macOS and Linux. Fix #728.

Key changes include:

• Automatic platform detection (mac, linux)
• Native command usage on macOS (e.g., sysctl, screencapture) and Linux (e.g., /proc/cpuinfo, scrot)
• Fallback to busybox commands for unsupported platforms
• Updated tests and configuration to use LocalTarget instead of platform-specific classes
• Maintained backward compatibility (LocalMacTarget remains as alias)

Benefits:

• Single class works on both macOS and Linux without manual selection
• Platform-specific logic centralized for easier maintenance
• Simplifies test configuration and improves code clarity

Let me know your thoughts. Happy to help.