Add a ping tester to check latency to different servers

[sudermanjr]

Example output:

└─ ./agones-allocator-client ping-test -t http://34.70.84.25,http://34.82.245.49
[
  {
    "host": "http://34.70.84.25",
    "dnsLookupTime": "0s",
    "response": "hurricane-1",
    "responseTime": "76.819223ms"
  },
  {
    "host": "http://34.82.245.49",
    "dnsLookupTime": "0s",
    "response": "tornado-1",
    "responseTime": "97.106097ms"
  }
]

responseTime is first connection to first byte
dnsLookupTime is the actual dns resolution time if you pass a hostname