When “Heated Rivalry ” became a viral phenomenon, everyone rushed to have their own version. Prime Video’s has entered the rink: “Off Campus.” Premiering May 13, the show has some cheesy moments, and a plot as fresh as month-old lettuce. But it’s also fun, charming, and addictively watchable – with more gravity than it looks like. Some characters have trauma backstories, in the middle of the rom-com fluff and steamy scenes. If you miss the heyday of CW shows, you’ll find a lot to like in “Off Campus.” “Hockey romance” is where its similarities to “Heated Rivalry” end, because “Off Campus” focuses on a heterosexual relationship, and it’s college sports, not the pros.…