Function: GetClassName(spawn)
Description: Gets the class name of the Spawn. In the Class Constant format in the classes table https://github.com/emagi/eq2emu/blob/main/docs/data_types/classes.md
Parameters:
spawn(Spawn) - Spawn object representingspawn.
Returns: String of the class name for the Spawn, using the Class Constant format (all upper case) in https://github.com/emagi/eq2emu/blob/main/docs/data_types/classes.md