MFC r367436 and r367443 by rew:

r367436
Add a periodic script to backup output generated from zfs list, zfs get,
zpool list, and zpool get commands.

Disabled by default.

r367443
Add a periodic script to backup output generated from gmirror list.

Disabled by default.

PR: 86388
Submitted by: Miroslav Lachman <000 dot fbsd at quip dot cz>
Reported by: Seklecki <Seklecki at FreeBSD dot org>
Reviewed by: allanjude, 0mp, gbe
Event: July 2020 Bugathon
Differential Revision: https://reviews.freebsd.org/D25638
Differential Revision: https://reviews.freebsd.org/D25631