[feature] Add script method to get ip address

[ricky9w]

Allow running custom scripts to get both IPv4 and IPv6 address by Python lib subprocess, and validate the output of custom scripts with lib ipaddress (all Python standard libraries)

Given that there will be three ways to obtain an IP address in the future, I have partially refactored the configuration file format. The new configuration file format is as follows:

"ip": {
    "a": {
      "enabled": true,
      "method": "http", // or "netif" or "script"
      "interface": "eth0", // interface name to get IPv4 address, used in interface mode
      "script": "script_v4.sh" // path to script to get IPv4 address
    },
    "aaaa": {
      "enabled": true,
      "method": "http",
      "interface": "eth0",
      "script": "script_v6.sh"
    }
  }

This is just a tentative configuration file scheme. Personally, I think that although it may seem a bit bulky, it looks clearer.