Previously, Jackson2ObjectMapperBuilder was a singleton bean. This
meant that if it was injected and mutated in one injection point,
usage in a subsequent injection point would see the previous
injection point's mutation which can lead to unexpected failures.

This commit updates the auto-configuration of the builder to make it
a protoype bean. Mutation of the builder that is intended to apply
globally should be made using a customizer.

Closes gh-17477