Prior to this commit, Module beans were registered with all
ObjectMapper beans, but were not registered with the auto-configured
Jackson2ObjectMapperBuilder. This meant that any ObjectMapper created
with the builder but not exposed as a bean would not have the Module
beans registered with it. One such ObjectMapper is the one used by the
auto-configured MappingJackson2XmlHttpMessageConverter. This caused
XML (de)serialization to be different to JSON (de)serialization.

This commit updates JacksonAutoConfiguration to register all of the
application context's Module beans with the auto-configured
Jackson2ObjectMapperBuilder. This ensures consistent configuration
of any ObjectMapper that's created using the builder, irrespective of
whether or not that ObjectMapper is also exposed as a bean, and
also ensures that (de)serialization of JSON and XML is consistent.

See gh-2327