plugins/amzn: Add stats support for EC2 local storage instance type

This patch adds the stats support for EC2 local storage on top of EBS.

For local storage, it supports a `--details / -d` option. In this mode
it will print out detail io histograms for different block size ranges.

Signed-off-by: Lingkai Zuo <[email protected]>

Author: lingkai0110