(Photo credit: Mark Allen/Barbican) What tenor Allan Clayton doesn’t know about misery probably isn’t worth knowing. His latest successes have been studies in anguish, specializing in alienated outsiders, or figures squatting on the borderland between life and death: Brett Dean’s “Hamlet,” “Peter Grimes” at the Royal Opera House Covent Garden and the Met, and, latterly for London audiences, a standout {…}