Federal prosecutors have charged three former top executives at Starkey Hearing Technologies and two other men with embezzlement and mail fraud, saying they conspired to steal $20 million from the hearing-aid maker over 10 years. The indictment, announced Wednesday, comes more than a year after Eden Prairie-based Starkey Hearing abruptly fired its president and several other top managers, setting off waves of accusations and lawsuits. Among those fired were former President Jerry Ruzicka, former…