Vdev Properties Feature

Add properties, similar to pool properties, to each vdev.
This makes use of the existing per-vdev ZAP that was added as
part of device evacuation/removal.

A large number of read-only properties are exposed,
many of the members of struct vdev_t, that provide useful
statistics.

Adds support for read-only "removing" vdev property.
Adds the "allocating" property that defaults to "on" and
can be set to "off" to prevent future allocations from that
top-level vdev.

Supports user-defined vdev properties.
Includes support for properties.vdev in SYSFS.

Co-authored-by: Allan Jude <allan@klarasystems.com>
Co-authored-by: Mark Maybee <mark.maybee@delphix.com>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Signed-off-by: Allan Jude <allan@klarasystems.com>
Closes #11711

cmd/zpool/zpool_util.h

@@ -65,7 +65,7 @@ nvlist_t *split_mirror_vdev(zpool_handle_t *zhp, char *newname,
 /*
  * Pool list functions
  */
-int for_each_pool(int, char **, boolean_t unavail, zprop_list_t **,
+int for_each_pool(int, char **, boolean_t unavail, zprop_list_t **, zfs_type_t,
     boolean_t, zpool_iter_f, void *);
 
 /* Vdev list functions */
@@ -73,7 +73,8 @@ int for_each_vdev(zpool_handle_t *zhp, pool_vdev_iter_f func, void *data);
 
 typedef struct zpool_list zpool_list_t;
 
-zpool_list_t *pool_list_get(int, char **, zprop_list_t **, boolean_t, int *);
+zpool_list_t *pool_list_get(int, char **, zprop_list_t **, zfs_type_t,
+    boolean_t, int *);
 void pool_list_update(zpool_list_t *);
 int pool_list_iter(zpool_list_t *, int unavail, zpool_iter_f, void *);
 void pool_list_free(zpool_list_t *);