The two Bay Area stars of the 2018 film “Blindspotting” — Daveed Diggs and Rafael Casal — are stepping away from the camera, or rather, behind it, to widen the lens in “Blindspotting” the TV series as executive producers, writers and showrunners, with an eight episode premiere season that will be available to stream on STARZ starting Sunday. We spoke with Casal about the production of the Oakland-set show.