Add rest API to retrieve cluster resource utilization

[
{
 partition: default,
 utilization: [ {
    type: "cpu",
    total: 100,
    used: 50,
    usage: 50%
  },
  {
     type: "memory",
     total: 1000,
     used: 500,
     usage: 50%
  }
 ]
}, 
...
]