Add per device rate metrics for instances

This change add pipline configuration support to gether per device
rate metrics for instance. The per device rate metrics for instances
is transform from the metrics of per devices for instances by adding
metrics to disk_pipline in pipline cfg. These metrics will be independent
of the support of per devices rate metrics provided by inspector.

This thange will add the following metrics:
  - "disk.device.read.bytes.rate"
  - "disk.device.read.requests.rate"
  - "disk.device.write.bytes.rate"
  - "disk.device.write.requests.rate"

Change-Id: I908ab40cc77966238944060e33603c5f4c440634
Merge "Add per device rate metrics for instances"