It’s billed as a comedy, and by most accounts, one of the year’s best. But for me, a survivor of the vicious jungle known as junior high school, Bo Burnham’s perceptive and deceptively deep “Eighth Grade” is a pure horror show.“Hereditary”? Tinker toys. “A Quiet Place”? Amateur hour. This, fright fans, is the stuff of shake-in-your-boots terror.