Add a "Skip Poll" Advice Class

Provide more flexibility over that provided by the Spring Trigger by providing an advice that can be configured on a Poller.

The advice should take an injected SkipPollStrategy (e.g. boolean shouldSkipPoll()).

This would allow, for example, the poller to look at a downstream task executor and only proceed with the poll if the executor has available threads (comparing maxPoolSize with activeCount ).

See the StackOverflow link for the use case.