core: services: helper: Add check_internet_access endpoint

[patrickelectric]

Allow frontend to check if the vehicle has internet access

Return:

{
  "ArduPilot": {
    "site": "http://firmware.ardupilot.org",
    "online": true,
    "error": null
  },
  "AWS": {
    "site": "http://amazon.com",
    "online": true,
    "error": null
  },
  "Cloudflare": {
    "site": "http://1.1.1.1/",
    "online": true,
    "error": null
  },
  "GitHub": {
    "site": "http://githubaaaaaaaaaaaa.com",
    "online": false,
    "error": "Cannot connect to host githubaaaaaaaaaaaa.com:80 ssl:default [Name or service not known]"
  }
}

[ES-Alexander]

• Helps Tell user if he has internet connection or not (somewhere) #1057

[joaoantoniocardoso]

LGTM