Christopher Reeve’s son Will Reeve revealed his testicular cancer diagnosis on Tuesday. The 34-year-old assured “Good Morning America” viewers “right off the top” that he is “OK” and battled the disease over the summer. “The diagnosis was a shock and the treatments were a slog,” he noted. “Today, though, I am relieved to announce that we arrived at our destination and this cancer is in the rearview mirror. But what a journey.” Will explained that four months after his January wedding to Amanda Dubin, he found “a hard, tender lump in [his] left testicle.” He went in for an ultrasound “at Amanda’s urging,” and “the images confirmed the…