Fix failfast default and usage

The feature that added a failfast property to vdevs unfortunately did
not correctly set the default at creation time, so many vdevs do not
actually have the property set. In addition, when the property is
used, the failfast flag is not checked correctly, resulting in the
feature mostly not working as intended.

Set the failfast property to the default value at vdev allocation time.
The value will be read in from the ZAP as normal when the vdev metadata
is loaded.  Allow the property to be set on any vdev and have it be
inherited from the root or top-level vdev.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Closes #18410

tests/runfiles/common.run

@@ -573,8 +573,8 @@ tags = ['functional', 'cli_root', 'zpool_scrub']
 
 [tests/functional/cli_root/zpool_set]
 tests = ['zpool_set_001_pos', 'zpool_set_002_neg', 'zpool_set_003_neg',
-    'zpool_set_ashift', 'zpool_set_features', 'vdev_set_001_pos',
-    'user_property_001_pos', 'user_property_002_neg',
+    'zpool_set_ashift', 'zpool_set_features', 'zpool_set_inherit',
+    'vdev_set_001_pos', 'user_property_001_pos', 'user_property_002_neg',
     'zpool_set_clear_userprop','vdev_set_scheduler']
 tags = ['functional', 'cli_root', 'zpool_set']