Breakdown reported times

[jeanbez]

• Add observed I/O time
• Add observed I/O rate
• Rename observed time to benchmark walltime/runtime
• Rename observed rate to benchmark rate
• Rename raw time to raw I/O time
• Rename raw rate to raw I/O rate
• Group metadata, raw I/O together, and improve overall groupping
• Ensure both CSV and output have these changes

[sbyna]

Rename observed rate to benchmark rate --> this is not needed.