The iocg can have three throttled metrics: wait, debt, delay. This patch
add missing wait_ms to IocgStat to show the latest wait_ms of iocg.

As we are here, group iocg usage percents "inflt%" and "usage%" together,
and group iocg throttled metrics "wait", "debt" and "delay" together.

Effect after changes:

nvme0n1 RUN  per=50.0ms cur_per=177105.713:v1053528.587 busy= +0 vrate=135.00%:270.00% params=ssd_dfl(CQ)
                          active    weight      hweight% inflt% usage%    wait    debt   delay
InterfererGroup0             *   100/  100  54.28/  9.09   0.34  24.07    0.00    0.00    0.00
interfered                   *    84/ 1000  45.72/ 90.91   0.48  41.09    0.00    0.00    0.00
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230804065039.8885-3-chengming.zhou@linux.devSigned-off-by: Jens Axboe <axboe@kernel.dk>