Standardize tablestats formatting and data units

Tablestats reports output in plaintext, JSON or YAML. The human readable output currently has a mix of KiB, bytes with inconsistent spacing

Simplify and default output to 'human readable'. Machine readable output is available as an option and the current mixed output formatting is neither friendly for human or machine reading and can be replaced.

Not a goal now (consider a follow up Jira):

Fix inconsistencies with KiB/MiB/GiB and KB/MB/GB formatting:

• gcstats - uses MB
• getcompactionthroughput - uses MB/s
• getstreamthroughput - uses MB/s
• info - uses MiB/GiB