JSON output support for zpool version

This commit adds support for zpool version to output in JSON format
using '-j' option. Userland kernel module version is collected in nvlist
which  is later displayed in JSON format. man page for zpool is updated.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Signed-off-by: Umer Saleem <usaleem@ixsystems.com>
Closes #16217

man/man8/zpool.8

@@ -38,6 +38,7 @@
 .Fl ?V
 .Nm
 .Cm version
+.Op Fl j
 .Nm
 .Cm subcommand
 .Op Ar arguments
@@ -79,10 +80,14 @@ Displays a help message.
 .It Xo
 .Nm
 .Cm version
+.Op Fl j
 .Xc
 Displays the software version of the
 .Nm
 userland utility and the ZFS kernel module.
+Use
+.Fl j
+option to output in JSON format.
 .El
 .
 .Ss Creation