INT-3328: Add `EnablePublisher` Annotation

JIRA: https://jira.spring.io/browse/INT-3328

INT-3328: Polishing
INT-3332 GlobalChannelInterceptorBeanPostProcessor

Implicit channel declaration for items downstream
of a `ChannelInterceptor` were not created.

The `BPP` eagerly fetched the interceptors during its
own creation; this caused the context initialization to fail
because the channel initializer hasn't run yet.

Defer creation of the interceptor beans until they are
actually needed.

Also, when using `@Configuration`, the channelInitializer
is no longer the first bean in the bean factory.

INT-3332 Use SmartLifeCycle to Apply Interceptors

Instead of using a bean post processor, the interceptor
processor now performs the channel interception when beans
in phase Integer.MIN_VALUE are started - after all beans
have been instantiated.

Polishing