testDurableData
Same query shape as testEphemeralData but using set_durable/2/get_durable/2: unlike ephemeral data, durable data survives backtracking, so both attempts at get_durable/2 succeed, binding X to 1.
Same query shape as testEphemeralData but using set_durable/2/get_durable/2: unlike ephemeral data, durable data survives backtracking, so both attempts at get_durable/2 succeed, binding X to 1.