samples/landlock: Add support for file reparenting

Add LANDLOCK_ACCESS_FS_REFER to the "roughly write" access rights and
leverage the Landlock ABI version to only try to enforce it if it is
supported by the running kernel.

Reviewed-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220506161102.525323-10-mic@digikod.net