Apple has hired Amazon exec William Stasior to run its Siri unit, according to a report from AllThingsD. With a doctoral degree from MIT, Stasior was recently in charge of A9, Amazon’s search and search advertising unit, which he co-founded, and previously served as an executive with AltaVista. Although Stasior will be in charge of Siri, the report speculates Stasior could also help to boost Apple’s search and search advertising technology.…