Previously it was possible to bind a bean to the root prefix by just
adding `@EnableConfigurationProperties` with the class of said bean.
This use case is misleading and prevents any meta-data to be generated
for that object since the annotation processor reacts on the presence of
the `@ConfigurationProperties` annotation.
If a class is included in the list of configuration properties bean to
create via the `@EnableConfigurationProperties` annotation we now make
sure that the `@configurationProperties` annotation is present on it.
Closes gh-3460
3740c817d3