What is the average lap time in milliseconds of all the lap records set on the various circuits in Italy?
average = AVG(milliseconds)
SELECT CAST(SUM(T1.milliseconds) AS REAL) / COUNT(T1.lap) FROM lapTimes AS T1 INNER JOIN races AS T2 on T1.raceId = T2.raceId INNER JOIN circuits AS T3 on T2.circuitId = T3.circuitId WHERE T3.country = 'Italy'