Given that they publicly announced her solo movie and we know she's coming to the MCU and are on the look out for her appearing, if they were going to cast Carol Danvers for Civil War it would be on super duper secret lock down. Even if they didn't straight up offer the role to Emily Blunt or some other known actress and it was an audition or screen testing process, they would try to keep it as secret as possible. They would certainly not put it on a casting call.