`ipfs dag stat` should return the compression ratio

[Jorropo]

Checklist

• My issue is specific & actionable.
• I am not suggesting a protocol enhancement.
• I have searched on the issue tracker for my issue.

Description

I would find neat if ipfs dag stat also displayed a float CumulatedSize (red from the block metadata when present) / Size (true size of IPFS blocks).
This would go below 1 for files that have a slight overhead due to roots taking up place.
And above 1 for things that reuse some blocks.

That is really easy to do as ipfs object stat already display the CumulatedSize.

The only thing I'm unsure if we want that, is the name, "compression ratio" sounds like we try to save space, while we don't it's mainly luck.