Added unit section to status endpoint #928

[Pavlusha311245]

Added unit section to /status endpoint. Unit section is about web-server version, config last load time and config update generation

Response example below:

{
  "unit": {
    "version": "1.32.0",
    "load_time": "2024-01-25T13:24:08.000Z",
    "generation": 0
  },
  "connections": {
    "accepted": 0,
    "active": 0,
    "idle": 0,
    "closed": 0
  },
  "requests": {
    "total": 0
  },
  "applications": {
    "laravel": {
      "processes": {
        "running": 1,
        "starting": 0,
        "idle": 1
      },
      "requests": {
        "active": 0
      }
    }
  }
}

Closes: https://github.com/nginx/unit/issues/928