polishing

This fixes a Java6 backward compatible issue introduced in the JCache
implementation.

This commit also adds new representative tests.

Issue: SPR-9616
fix CI build

Prior to this commit, AnnotatedJCacheableService contained an annotated
method demonstrating a failure scenario. This could break depending on
the order of the methods array as AopUtils creates the proxy if the
pointcut matches by checking each method.

On the CI server, the first method was this invalid use case so
checking if the proxy has to be created lead to an unexpected
exception. This scenario has been moved to its own private class now.