Implement native Windows network interface enumeration

[LunaStev]

Motivation

The public network interface API routes to a Windows provider whose interfaces_open always returns -95; the remaining accessor functions are stubs. Windows amd64/ARM64 applications cannot enumerate local interface addresses through the portable API. This is separate from Linux's getifaddrs replacement (#566).

Starting points: std/sys/windows/interfaces.wave, std/sys/interfaces.wave, std/net/interface.wave.

Scope

Implement a Windows-native provider, for example using GetAdaptersAddresses, while preserving the public output-buffer API. Define how Windows adapter identity, display names, flags and address families map to NetworkInterface. Cover native allocation ownership and the required import library; no libc adapter is needed. Related Windows provider tracker: #385.

Difficulty: hard.

Completion criteria

• Enumerate IPv4/IPv6 addresses with correct indices, names and result counts on amd64/ARM64.
• Handle no addresses, buffer growth, capacity truncation and native errors without leaking memory.
• Mock fixtures cover multiple addresses per adapter and Unicode names; native tests avoid assuming a particular machine network configuration.

Design decision needed: Agree on stable interface identity/name encoding and flag mappings, including truncation behavior, before implementing the provider.

Please mention @LunaStev to discuss the design before starting implementation.