Spring Allow builder to set constructor detector for object mapper

This is to allow the Jackson Object Mapper Builder to be able to accept a constructor detector. The idea is that it can then be used by this to configure it via properties.

see gh-27178

Comment From: snicoll

@SatsG thank you for your first PR to the spring framework (very complete I should say!). Unfortunately, ConstructorDetector is new in Jackson 2.12 and we need to keep runtime compatibility to Jackson 2.9 still.

The issue you referred to can be implemented in any case as the builder exposes a customizer you can use to access the ObjectMapper before it is returned, see postConfigurer.