tests: add test for vdev_disk page alignment check

This provides a test driver and a set of test vectors for the page
alignment check callback function vdev_disk_check_pages_cb().

Because there's no good facility for exposing this function to a
userspace test right now, for now I'm just duplicating the function and
adding commentary to remind people to keep them in sync.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Closes #16076

tests/runfiles/common.run

@@ -971,6 +971,12 @@ tests = [
     'userspace_send_encrypted', 'userspace_encrypted_13709']
 tags = ['functional', 'userquota']
 
+[tests/functional/vdev_disk:Linux]
+pre =
+post =
+tests = ['page_alignment']
+tags = ['functional', 'vdev_disk']
+
 [tests/functional/vdev_zaps]
 tests = ['vdev_zaps_001_pos', 'vdev_zaps_002_pos', 'vdev_zaps_003_pos',
     'vdev_zaps_004_pos', 'vdev_zaps_005_pos', 'vdev_zaps_006_pos',

tests/runfiles/sanity.run

@@ -599,6 +599,12 @@ tags = ['functional', 'truncate']
 tests = ['upgrade_userobj_001_pos', 'upgrade_readonly_pool']
 tags = ['functional', 'upgrade']
 
+[tests/functional/vdev_disk:Linux]
+pre =
+post =
+tests = ['page_alignment']
+tags = ['functional', 'vdev_disk']
+
 [tests/functional/vdev_zaps]
 tests = ['vdev_zaps_001_pos', 'vdev_zaps_003_pos', 'vdev_zaps_004_pos',
     'vdev_zaps_005_pos', 'vdev_zaps_006_pos']