Add GDB Machine Interface adapter for local debugging

[Copilot]

This PR implements a new GDB Machine Interface (MI) adapter that provides local debugging capabilities using GDB's structured MI protocol, complementing the existing remote-only GDB RSP adapter.

Key Features

Local Debugging Support: Unlike the existing GdbAdapter which only supports remote connections, the new GdbMiAdapter provides full local process execution via Execute() and ExecuteWithArgs() methods.

Structured Communication: Uses GDB's Machine Interface protocol instead of raw Remote Serial Protocol packets, providing better parsing, error handling, and structured responses.

System Integration: Automatically detects system GDB installations with fallback support for bundled GDB executables. Validates MI support and provides clear error messages when requirements aren't met.

Cross-Platform Support: Includes comprehensive process management for Windows, macOS, and Linux with proper pipe handling and process lifecycle management.

Implementation

The adapter is implemented as:

• GdbMiAdapter: Main adapter class inheriting from DebugAdapter with full MI protocol support
• GdbMiAdapterType: Adapter type class with system validation and capability detection
• Automatic Registration: Appears as "GDB MI (Local)" in the debugger adapter selection

Architecture

Binary Ninja UI ←→ GdbMiAdapter ←→ System GDB (--interpreter=mi) ←→ Target Process
                        ↓
                   Bundled gdbserver (for enhanced features)

Changes Made

• New Files: core/adapters/gdbmiadapter.{h,cpp} with complete MI implementation
• Build Integration: Updated CMakeLists.txt to include new adapter and properly bundle gdbserver
• Registration: Modified core/debugger.cpp to initialize the new adapter type

Differences from Existing GdbAdapter

Feature	GdbAdapter (RSP)	GdbMiAdapter (MI)
Protocol	Remote Serial Protocol	Machine Interface
Local Execution	❌ Remote only	✅ Full local support
Communication	Raw packets	✅ Structured responses
Requirements	gdbserver bundle	System GDB + gdbserver

The implementation provides comprehensive debugging capabilities including breakpoints, stepping operations, memory access, register management, and reverse debugging support through GDB's rich MI interface.

Fixes #170.

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