Reinstate Jackson 2.x support as fallback #1236
Description
When upgrading to Spring Framework 7.0 in #1202, we went directly to Jackson 3.0 support and removed any Jackson 2.x support. We should reinstate Jackson 2.x support as a fallback with the proper deprecation warnings.
For now, Spring Framework intends to fade out Jackson 2.x in the next minor releases and so should we.