Fix tests that depend on previous Spring Boot config issue #2042
Description
The build is failing since an issue was fixed in spring-projects/spring-boot@f2b3f1f that our tests took advantage of in order to disable R2DBC auto-configuration, see: https://github.com/spring-cloud/spring-cloud-sleuth/runs/3956427697
I think having public config classes in ConnectionFactoryConfigurations would be better so that we can exclude them.