This is a parallel track to https://github.com/openzfs/openzfs/pull/600 to get
more reviews and, possibly, speedier adoption in FreeBSD. Specifically, I
would appreciate any help on improving the manual page changes.
The changes come from ZoL.
The porting has been done by @julian.
The change adds -t <name> option zpool create and -t option to zpool import in
its form with an old name and a new name. This allows to import (or create) a
pool under a name that's different from its real, permanent name without
affecting that name. This is useful when working with VM images or images of
other physical systems if they happen to have a ZFS pool with the same name as
the host system.