Raise MessageConversionException in @Payload resolver

If a payload is present but conversion returns null (meaning no
converter knows how to convert), raise a MessageConversionException
that provides information about the type we were trying to convert
to and the message itself whose headers (namely content-type) contain
crucial information required to debug the problem.

Issue: SPR-11577
Javadoc: @ComponentScan is subject to @Conditional as well

Issue: SPR-11579
BufferedImageHttpMessageConverter ignores empty MIME types

Issue: SPR-11581
Polish ASM-based annotation processing

- AnnotationAttributesReadingVisitor no longer processes annotations
  from the java.lang.annotation package.

- Simplified logic in AnnotationReadingVisitorUtils
  getMergedAnnotationAttributes().

Issue: SPR-11574