feat: support Windows TUN mode

[kitty-eu-org]

Added TUN mode support for Windows to enable transparent proxying. This implementation covers interface creation and basic routing setup.

[happytrudy]

Has there been any progress on this issue?

[cfal]

i think this PR was mainly written by AI without quite understanding the consequences - and i can't tell whether the tun changes are correct and if they break anything on Linux which was just recently fixed. I'm curious if the entire event loop in run_tun_server actually needs to be changed to support Windows.

[cfal]

any reason for rename?

[kitty-eu-org]

The tun-rs library now supports asynchronous mode, so I want to convert all the code to be uniformly asynchronous. Additionally, Windows does not support file descriptors (fd), so I implemented a VirtTunDeviceand channel by referring to the implementation in shadowsocks-rust. This unavoidably leads to substantial changes to your original code.

[kitty-eu-org]

i think this PR was mainly written by AI without quite understanding the consequences - and i can't tell whether the tun changes are correct and if they break anything on Linux which was just recently fixed. I'm curious if the entire event loop in run_tun_server actually needs to be changed to support Windows.

I have indeed used AI to write a lot of code, but I have tested it on Windows and confirmed that tun works properly. It has also been tested on Linux and works correctly