Not only is summer a useful time to finish or delete anything that’s loitering in your DVR, I’ve always encouraged viewers to also use these months as a time to guiltlessly graze TV’s junk-food aisles. Certain inane pleasures await when we stop treating TV like highbrow homework and let it become the populist entertainer it was made to be. That said, I do have some summer assignments (no groaning!), including FX’s instantly addictive 1980s drug epic “Snowfall” (July 5), Netflix’s delightful lady-wrestler dramedy “GLOW” (June 23) and PBS’ ace-detective prequel “Prime Suspect: Tennison” (June 25). And here are another 20 new and returning shows I think are worth checking out between now and Labor Day.