fix(sslocal): disallow HTTP/SOCKS4 proxying when authentication required

[alaz]

Testing

The same set of tests as in #1764

config.json

{
    "locals": [
        {
            "protocol": "socks",
            "local_address": "127.0.0.1",
            "local_port": 9090,
            "socks5_auth_config_path": "auth.json"
        }
    ],

    "servers": [
            {...}
    ],
}

auth.json:

{
    "password": {
        "users": [
            {
                "user_name": "user",
                "password": "password"
            }
        ]
    }
}

Tests:

$ curl -si --proxy socks5://127.0.0.1:9090 -U user:password https://api.seeip.org | head -4
HTTP/1.1 200 OK
Server: nginx/1.18.0 (Ubuntu)
Date: Mon, 11 Nov 2024 17:38:29 GMT
Content-Type: text/plain

$ curl -i --proxy socks5://127.0.0.1:9090 -U user:pass https://api.seeip.org 
curl: (97) User was rejected by the SOCKS5 server (1 255).

$ curl -i --proxy http://127.0.0.1:9090 -U us:pass https://api.seeip.org 
curl: (56) Recv failure: Connection reset by peer