arcstat: Add -a and -p options from FreeNAS

Added -a option to automatically print all valid statistics.
Added -p option to suppress scaling of printed data.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Authored by: Nick Principe <32284693+powernap@users.noreply.github.com>
Ported-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #11090

man/man1/arcstat.1

@@ -13,13 +13,13 @@
 .\" Copyright (c) 2015 by Delphix. All rights reserved.
 .\" Copyright (c) 2020 by AJ Jordan. All rights reserved.
 .\"
-.TH ARCSTAT 1 "Aug 24, 2020" OpenZFS
+.TH ARCSTAT 1 "Oct 20, 2020" OpenZFS
 .SH NAME
 arcstat \- report ZFS ARC and L2ARC statistics
 .SH SYNOPSIS
 .LP
 .nf
-\fBarcstat\fR [\fB-hvx\fR] [\fB-f field[,field]...\fR] [\fB-o file\fR] [\fB-s string\fR] [\fBinterval\fR [\fBcount\fR]]
+\fBarcstat\fR [\fB-havxp\fR] [\fB-f field[,field]...\fR] [\fB-o file\fR] [\fB-s string\fR] [\fBinterval\fR [\fBcount\fR]]
 .fi
 
 .SH DESCRIPTION
@@ -510,6 +510,15 @@ May temporarily be negative, in which case the ARC will reduce the target size \
 .LP
 The following options are supported:
 
+.sp
+.ne 2
+.na
+\fB\fB-a\fR\fR
+.ad
+.RS 12n
+Print all possible stats.
+.RE
+
 .sp
 .ne 2
 .na
@@ -537,6 +546,15 @@ Display help message.
 Report statistics to a file instead of the standard output.
 .RE
 
+.sp
+.ne 2
+.na
+\fB\fB-p\fR\fR
+.ad
+.RS 12n
+Disable auto-scaling of numerical fields (for raw, machine-parsable values).
+.RE
+
 .sp
 .ne 2
 .na