Implement a new type of zfs receive: corrective receive (-c)

This type of recv is used to heal corrupted data when a replica
of the data already exists (in the form of a send file for example).
With the provided send stream, corrective receive will read from
disk blocks described by the WRITE records. When any of the reads
come back with ECKSUM we use the data from the corresponding WRITE
record to rewrite the corrupted block.

Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Paul Zuchowski <pzuchowski@datto.com>
Signed-off-by: Alek Pinchuk <apinchuk@axcient.com>
Closes #9372

include/sys/zio.h

@@ -534,6 +534,8 @@ extern zio_t *zio_null(zio_t *pio, spa_t *spa, vdev_t *vd,
 extern zio_t *zio_root(spa_t *spa,
     zio_done_func_t *done, void *priv, enum zio_flag flags);
 
+extern void zio_destroy(zio_t *zio);
+
 extern zio_t *zio_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
     struct abd *data, uint64_t lsize, zio_done_func_t *done, void *priv,
     zio_priority_t priority, enum zio_flag flags, const zbookmark_phys_t *zb);