This mainly removes logic where no fields were included in the debug output if "w" was equal to MONGOC_WRITE_CONCERN_W_DEFAULT.
Although the "wmajority" boolean exists, we can still report the actual "w" value, which will be sent to the server.
The purpose is two-fold: abstract libmongo'c constant (defined as -3) from our users and ensure the string "majority" is sets the struct's "w" field properly even if our constant is not used.