Revise AspectJ examples in the reference manual

[sbrannen]

As stated in #29998 (comment), the extensive use of shared pointcuts can be confusing to users who read a given AspectJ example without having read the the Sharing Common Pointcut Definitions section of the AOP chapter.

We should therefore reassess the extent to which we use shared pointcuts in subsequent examples and/or cross reference the Sharing Common Pointcut Definitions section.