This Statement is true. During the final moments of his Netflix special, Chris Rock talks about how he is not crying about the Will Smith slap during the Oscars. According to Yahoo Life News, Chris Rock stated "But I’m not a victim, baby." They quoted that he said, "You’ll never see me on Oprah or Gayle crying. You will never see it. Never gonna happen. … No, I took that hit like [Manny] Pacquiao.”
In regards to the claim that Jada Smith had a relationship with her son's friend is true. It's true that he said it during his special but, we don't know for sure if it is actually true. According to the article, Chris stated, "His wife was fucking her son’s friend." He continues to go on and states that everyone says mean things about Will but he decides to hit him.
Based on this research, I would say that the claim is overall true.
https://www.yahoo.com/lifestyle/chris-rock-finally-addressed-smith-215110840.html?fr=sycsrp_catchall