Update arc_summary and arcstat outputs

Update arc_summary and arcstat outputs

Recent ARC commits added new statistic counters, such as iohits,
uncached state, etc.  Represent those.  Also some of previously
reported numbers were confusing or even made no sense.  Cleanup
and restructure existing reports.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:  Alexander Motin <mav@FreeBSD.org>
Sponsored by:   iXsystems, Inc.
Issue #14115
Issue #14123
Issue #14243
Closes #14320