MSNBC made it official today, announcing that Joy Reid will host a new weekend program on Saturdays and Sundays 10 AM-Noon ET, starting May 7. Yes, that’s the timeslot formerly held by MHP, hosted by Melissa Harris-Perry, who left in a hail of tweets and emails after refusing to return to the slot to host election-cycle coverage, saying she was “not hungry for empty airtime.” Reid’s untitled show will “tackle the most important news and political topics of the week and…