If you haven’t seen any Jackass movie before and are curious if you should try it, here’s a very simple test: Do you not mind the idea of seeing grown adults get tossed around in a porta-potty, stung in the lips by a scorpion, or hit in the testicles in new ways you might have thought impossible? If those things don’t necessarily appeal to you, you may not like Jackass Forever, but this may be the crew that sells you on the value of low-brow humor because these guys are the best to ever do it. In the new movie Jackass Forever, filmed over 10 years after the series’ third installment, Johnny Kn…