Extend zpool-iostat to account for ZIO_PRIORITY_REBUILD (#12319)

Previously, zpool-iostat did not display any data regarding rebuild I/Os
in either the latency/size histograms (-w/-l/-r) or the queue data (-q).
This fix essentially utilizes the existing infrastructure for tracking
rebuild queue data and displays this data in the proper places within
zpool-iostat's output.

Signed-off-by: Trevor Bautista <tbautista@newmexicoconsortium.org>
Signed-off-by: Trevor Bautista <tbautista@lanl.gov>
Co-authored-by: Trevor Bautista <tbautista@newmexicoconsortium.org>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>