Index disk utilization statistics

Description:

The index disk utilization metrics on the Admin UI do not match with the actual disk utilization. The UI metrics don't consider the amount of junk data in for a specific index but the disk utilization does include the same.

Having another UI metric that indicates the amount of junk data would help end users to understand when the index would be compacted and the fragmentation levels for every index.

This will also help explaining the disk utilization of a specific index and help the customers size their disks accordingly.