Prior to this commit, ClassWithAsyncAnnotation#return5 forced an
unsuppressable warning in Eclipse, making it virtually impossible to
get to a zero-warnings state in the codebase.
The 'solution' here is simply to comment out the method and it's
associated test case. The 'declare warnings' functionality around
@Async is well-understood and has long been stable.
Also, the entire AnnotationAsyncExecutionAspectTests class has been
added to TestGroup#PERFORMANCE (SPR-9984), as opposed to just
asyncMethodGetsRoutedAsynchronously as it was previously, the
rationale being that all tests are actually timing dependent.
Issue: SPR-9431, SPR-9984