Support Pointer Authentication (PAC) for ARM64e

[mingxwa]

The current implementation of proxy relies on function pointers for dispatching calls to the underlying objects. On ARM64e architectures (e.g., Apple Silicon, newer ARM server chips), these indirect branches are potential targets for ROP/JOP attacks if not properly protected. Without Pointer Authentication Code (PAC) support, the library misses a critical hardware-enforced security feature available on modern platforms.

This is a security hardening feature. As proxy is designed for high-performance and system-level usage (including potential kernel design), leveraging hardware security features like PAC is essential for modern deployment environments.