zfs: bring back possibility to rewind the checkpoint from

Add parsing of the rewind options.

When I was upstreaming the change [1], I omitted the part where we
detect that the pool should be rewind. When the FreeBSD repo has
synced with the OpenZFS, this part of the code was removed.

[1] FreeBSD repo: 277f38abffc6a8160b5044128b5b2c620fbb970c
[2] OpenZFS repo: f2c027bd6a003ec5793f8716e6189c389c60f47a

Originally reviewed by: tsoome, allanjude
Originally reviewed by: kevans (ok from high-level overview)

Signed-off-by: Mariusz Zaborski <oshogbo@vexillium.org>

PR: 254152
Approved by: re(gjb)
Reported by: Zhenlei Huang <zlei.huang at gmail.com>
Obtained from: https://github.com/openzfs/zfs/pull/11730

(cherry picked from commit 653ed678c70376b15cdc42daafa7b4554570cea2)
(cherry picked from commit 6bbca5ca3a6634fc10b93da203df2ae92cf60b61)