By Pascal Rossignol BOULOGNE-SUR-MER, France (Reuters) -France on Saturday seized a car cargo ship in the English Channel that Washington says was linked to the son of a former Russian spy chief, in one of the first visible displays of the West enforcing sanctions on Moscow over its Ukraine invasion. The “Baltic Leader” was headed to St. Petersburg but was diverted to the port of Boulogne-sur-Mer in northern France between 3 a.m. and 4 a.m. (0200-0300 GMT), Captain Veronique Magnin of the French Maritime Prefecture told Reuters. The vessel was “strongly suspected of being linked to Russian int…