By Jason Buch, Evan Garcia and Ted Hesson SAN ANTONIO (Reuters) -At least 50 migrants died after being stuck inside a sweltering semi-trailer in San Antonio, U.S. and Mexican officials said on Tuesday, in one of the deadliest human trafficking incidents in recent history. The migrants were discovered dead inside the truck’s trailer on the outskirts of the Texas city on Monday, where temperatures swelled to a high of 103 Fahrenheit (39.4 Celsius). Authorities responded to a remote area in the south part of the city and found the truck parked next to railroad tracks. Bodies were strewn over a co…