A reliance on guest stars and gimmicks often means a popular TV series has “jumped the shark” — a way of saying the show’s writers and directors have exhausted themselves creatively. The funny thing about “Only Murders in the Building,” the Emmy-nominated comedy series about mysterious deaths at a New York apartment residence, is that right from the start, the show frequently featured daft tangents and guest stars as disparate as Sting, Nathan Lane, and Tina Fey.