Possibility to physically reserve space without writing leaf blocks

*** 304,313 ****
--- 304,314 ----
          uint8_t                 zp_level;
          uint8_t                 zp_copies;
          boolean_t               zp_dedup;
          boolean_t               zp_dedup_verify;
          boolean_t               zp_nopwrite;
+         boolean_t               zp_zero_write;
  } zio_prop_t;
  
  typedef struct zio_cksum_report zio_cksum_report_t;
  
  typedef void zio_cksum_finish_f(zio_cksum_report_t *rep,