SpringBoot Make ConfigDataLocation.of non-nullable

org.springframework.boot.context.config.ConfigDataLocation#of should never return null. Instead of the return null, we should throw an exception.

Comment From: mhalbritter

If we throw an exception, we break https://github.com/spring-projects/spring-boot/issues/26342.

This branch explores returning a null object: https://github.com/mhalbritter/spring-boot/tree/mh/make-configdatalocation-of-non-nullable