9466 add JSON output support to channel programs

illumos/illumos-gate@5267591016146502784860802129b16dab6f135c

Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed by: Sara Hartse <sara.hartse@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Alek Pinchuk <apinchuk@datto.com>