“Sierra Burgess Is a Loser,” which released Friday on Netflix, feels like a glorified, slightly higher-budget Disney Channel original movie. And as much as I love “High School Musical,” that’s certainly not a compliment. Borderline unwatchable at worst and a hesitant guilty pleasure at best, “Sierra Burgess Is a Loser” tells the story of Sierra, an awkward high school girl who finds herself in an unexpected romance after her classmate, popular cheerleader Veronica, gives Sierra’s number to Jamey, the quarterback of another local high school.