SpringBoot Register Couchbase's JsonValueModule to ObjectMapper in CouchbaseAutoConfiguration

Fixes #26363

• Copy the ObjectMapper that gets configured by Spring Boot to create a new ObjectMapper
• Register Couchbase's JsonValueModule to the new ObjectMapper

Comment From: wilkinsona

Thanks for the PR, @nguyensach. As mentioned in #26363, the most important thing for the fix was to verify that Couchbase could serialise and deserialise JSON. I've done that in https://github.com/spring-projects/spring-boot/commit/b1f3d91f7df5dd311bf7e835cf6df003865a069c while also verifying that all of the auto-configured ObjectMapper's modules are still registered in addition to the JsonValueModule. Thanks anyway.