pf tests: add tests for the new scrub syntax
Add functions for testing new scrub option syntax and for packet
fragmentation and route tables, because this was modified too. When
testing of both the new and the compatible syntax is necessary, move
original tests into _compat.sh file.
Reviewed by: kp
Sponsored by: InnoGames GmbH
Differential Revision: https://reviews.freebsd.org/D38129