Cleanup `--debug-operations`

[Fizzadar]

It's super helpful and yet the output is... painful? Few thoughts:

• Output command bits (Fix mysql load command #922 (comment))
• Optionally dump out proper JSON so it can be used elsewhere, to stdout (similar: Add --json output flag #509)
• Don't separate operation meta & commands, makes it really hard to see what's going on
• When not outputting JSON, make the output actually readable, make it very clear what is to run on each host