feature: device add support unixsocket use fd

[lflish]

This is a great project.
For ease of use, I gave it a little detail.
Using FD is compatible with all Linux communication, and I optimized it to use Unix sockets directly，It has no effect on the original method

device: unix:///tmp/unix_socket

[xjasonlyu]

Hi! Thanks for your PR.

Unix socket can be a great source input for tun2socks project. Can we implement it in the core/device pkg directly?

[lflish]

你好
新改的代码放到了core/device目录了，但是对设备解析的函数parseDevice中， url.Parse(s)函数对unix:///tmp/unix.sock这种格式解析有问题，所以把这里也重新写了下。

	devInfo := strings.Split(s, "://")
	if len(devInfo) < 2 {
		return nil, fmt.Errorf("unsupported device: %s", s)
	}
	driver, name := devInfo[0], devInfo[1]

[xjasonlyu]

There is actually no issue with this parsing process, you don’t need u.Host, just use u.Path directly.

[lflish]

多谢指点，这块代码回滚重新提交了