fix(aws): allow enabledMetrics: [] to enable all metrics

[dbyron-sf]

when building an auto scaling group. https://docs.aws.amazon.com/autoscaling/ec2/APIReference/API_EnableMetricsCollection.html says:

If you specify Granularity and don't specify any metrics, all metrics are enabled.

Before this change

  enabledMetrics: []

in a deploy stage would enable no metrics, like this:

$ aws autoscaling describe-auto-scaling-groups --region=us-west-2 --auto-scaling-group-names=my-asg-v001 | jq .AutoScalingGroups[0].EnabledMetrics
[]

After this PR, we get:

$ aws autoscaling describe-auto-scaling-groups --region=us-west-2 --auto-scaling-group-names=my-asg-v002 | jq .AutoScalingGroups[0].EnabledMetrics
[
  {
    "Metric": "GroupInServiceInstances",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupAndWarmPoolDesiredCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupTerminatingCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "WarmPoolMinSize",
    "Granularity": "1Minute"
  },
  {
    "Metric": "WarmPoolWarmedCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupTotalInstances",
    "Granularity": "1Minute"
  },
  {
    "Metric": "WarmPoolTotalCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupAndWarmPoolTotalCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupDesiredCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupPendingCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupStandbyInstances",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupPendingInstances",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupMinSize",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupStandbyCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupTotalCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "WarmPoolDesiredCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "WarmPoolPendingCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupTerminatingInstances",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupInServiceCapacity",
    "Granularity": "1Minute"
  },
  {
    "Metric": "GroupMaxSize",
    "Granularity": "1Minute"
  },
  {
    "Metric": "WarmPoolTerminatingCapacity",
    "Granularity": "1Minute"
  }
]

[jasonmcintosh]

enabledMetrics - looks like if NOT set this would be null and disable them. Looking a bit more to see if that's the default or if blank was default (or if deck set a blank kinda thing)

[dbyron-sf]

I did a test with no mention of enabledMetrics in the deploy and didn’t get any metrics….The default looks like implicit null here which I think is what does the trick.