pfctl: Move to DIOCADDRULENV

Start using the new nvlist based ioctl to add rules.

MFC after: 4 weeks
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D29558

(cherry picked from commit 5c11c5a3655842a176124ef2334fcdf830422c8a)