geli tests: Add a regression test for geli setkey -J

Make sure that it can be used to change the passphrase of both attached
and detached providers.

Approved by: re (kib)
PR: 254966
MFC after: 1 week
Sponsored by: The FreeBSD Foundation

(cherry picked from commit 2b7b09ac9675023869fddbae4911c9b674b1155a)