iocost_monitor: Report more info with higher accuracy

When outputting json:

* Don't truncate numbers.

* Report address of iocg to ease drilling down further.

When outputting table:

* Use math.ceil() for delay_ms so that small delays don't read as 0.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>