perf(macos): speed up interface enumeration

[shellrow]

Summary

Improves interface enumeration performance on macOS.

What changed

• Parse SystemConfiguration/NetworkInterfaces.plist directly to get extra info
  • Fallback to SystemConfiguration::SCNetworkInterfaceCopyAll if plist parsing fails (compatibility/safety net)
• Added functional-interface-type lookup using SIOCGIFFUNCTIONALTYPE ioctl
• Merge the parsed result into unix_interfaces() output

Performance

Measured on my machine (22 interfaces):

Before (release):

• Total time: ~13–15 ms
• SCNetworkInterfaceCopyAll: ~12–14 ms

After (release):

• Total time: ~1.9–2.0 ms
• Plist parse + merge: ~0.3 ms

Scope

• macOS only (includes internal refactor shared with iOS)
• No API changes

[dignifiedquire]

I can confirm the speedup of listing interfaces (currently 23 on my machine) with this PR