The income have been multiplying at a dizzying clip: 50%, 100%, then all of a sudden nearly 200%. Even for long-time veterans at Attestor Ltd., a boutique London agency that makes a speciality of buying and selling distressed belongings, this had the makings of a rating to recollect.The commerce — concentrating on the stays of Sam Bankman-Fried’s once-vast cryptocurrency empire — turned a well-liked one in distressed investing circles final yr.