Auto-configure SmileMapper.Builder and SmileMapper

[quaff]

Smile should be supported as same as CBOR, like Spring Framework's DefaultHttpMessageConverters does.

https://github.com/spring-projects/spring-framework/blob/5e213b2407bc211aee4bfa02f5e1909128860f2f/spring-web/src/main/java/org/springframework/http/converter/DefaultHttpMessageConverters.java#L146

[wilkinsona]

Thanks for the PR, @quaff. I'm not sure that it should be the same. Unlike XML and CBOR, Spring Boot's never had any built-in Smile support and Jackson2ObjectMapperBuilder doesn't have a createSmileMapper method. We can consider adding it in the future, but I think we should wait until there's obvious demand for it rather than doing it purely to be the same a CBOR.