SpringBoot PubSub Example House Cleaning

[cicoyle]

We should move the spring boot pubsub example to java-sdk/spring-boot-example/pubsub then have the producer/consumer apps inside that folder. We should also have it purely be about a pubsub example. We should not mix workflows and pubsub in this example. This will align with the java-sdk pattern of having examples in a folder, then showing per API examples in this manner