Add host OS statistics to the kcli top command

[MHillyer]

As a user of the kcli top command, I want to add context to the data I'm seeing about server behaviors.

In addition to seeing data such as queue depth, I want to see its impact on the server resources such as IOwait, memory usage/swap, and CPU load.

[wez]

Note that we already show memory usage in kcli top.

re: iowait, is that actually a useful metric? That's the cumulative time spent waiting on IO.
All our IO is asynchronous and non-blocking wrt. to the initiator, so the iowait
number will be misleading and hard to correlate meaningfully.

If IO is an issue, it will make much more sense to break out appropriate tools such as iotop.
I want to avoid trying to recreate something like iotop here; we cannot do better,
and iotop requires root or NET_ADMIN privileges to run, which we do not have
in kumod.