MFC r367436 and r367443 by rew:

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