pf: Simplify rule actions logic

Actions applied to a processed packet come in case of stateless
firewalling from a rule or in case of statefull firewalling from a
state. The state obtains the actions from a rule when it is created by a
rule or by pfsync. The logic for deciding if actions come from a rule or
a state is spread across many places in pf.

There already is struct pf_rule_actions in struct pf_pdesc and thus it
can be used as a central place for storing actions and their parameters.
OpenBSD does something similar: they also store the actions in struct
pf_pdesc and have no variables in pf_test() but they use separate
variables instead of a structure. By using struct pf_rule_actions we can
simplify the code even further. Applying of actions is done *only* in
pf_rule_to_actions() no matter if for the legacy scrub rules or for the
normal match / pass rules. The logic of choosing if rule or state
actions are used is applied only once in pf_test() by copying the whole
struct.

Reviewed by: kp
Sponsored by: InnoGames GmbH
Differential Revision: https://reviews.freebsd.org/D41009