pf: Introduce nvlist variant of DIOCADDRULE
This will make future extensions of the API much easier.
The intent is to remove support for DIOCADDRULE in FreeBSD 14.
Reviewed by: markj (previous version), glebius (previous version)
MFC after: 4 weeks
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D29557