To ride the horses from England, Ireland and France, which raced in the Laurel International last week, came some of Europe's finest jockeys. Willie Snaith, 26, looking like a pocket version (if possible) of Mickey Rooney, was on hand to ride the Queen's Landau. From Paris came the veteran Rae Johnstone, 49, the Arcaro of foreign turf racing, who has ridden in 10 countries, won nearly 2,000 times. Johnstone is called "The Crocodile" for his habit of coming from behind to eat up the opposition. But at Laurel it was Arcaro who gobbled up tactical honors.