Added ephemeral_storage_node_* metrics

[jmcgrath207]

New metric type ephemeral_storage_node_* and granular control of metrics.

# HELP ephemeral_storage_adjusted_polling_rate AdjustTime polling rate time after a Node API queries in Milliseconds
# TYPE ephemeral_storage_adjusted_polling_rate gauge
ephemeral_storage_adjusted_polling_rate{node_name="ephemeral-metrics-cluster-control-plane"} 14977
ephemeral_storage_adjusted_polling_rate{node_name="ephemeral-metrics-cluster-worker"} 14978
# HELP ephemeral_storage_node_available Available ephemeral storage for a node
# TYPE ephemeral_storage_node_available gauge
ephemeral_storage_node_available{node_name="ephemeral-metrics-cluster-control-plane"} 6.37831856128e+11
ephemeral_storage_node_available{node_name="ephemeral-metrics-cluster-worker"} 6.37831856128e+11
# HELP ephemeral_storage_node_capacity Capacity of ephemeral storage for a node
# TYPE ephemeral_storage_node_capacity gauge
ephemeral_storage_node_capacity{node_name="ephemeral-metrics-cluster-control-plane"} 9.83036076032e+11
ephemeral_storage_node_capacity{node_name="ephemeral-metrics-cluster-worker"} 9.83036076032e+11
# HELP ephemeral_storage_node_percentage Percentage of ephemeral storage used on a node
# TYPE ephemeral_storage_node_percentage gauge
ephemeral_storage_node_percentage{node_name="ephemeral-metrics-cluster-control-plane"} 64.88387066145039
ephemeral_storage_node_percentage{node_name="ephemeral-metrics-cluster-worker"} 64.88387066145039

values.yaml

metrics:
  # -- Current ephemeral byte usage of pod
  ephemeral_storage_pod_usage: true
  # -- Available ephemeral storage for a node
  ephemeral_storage_node_available: true
  # -- Capacity of ephemeral storage for a node
  ephemeral_storage_node_capacity: true
  # -- Percentage of ephemeral storage used on a node
  ephemeral_storage_node_percentage: true
  # -- Create the ephemeral_storage_adjusted_polling_rate metrics to report Adjusted Poll Rate in milliseconds. Typically used for testing.
  adjusted_polling_rate: false