INT-3545: Don't AutoStart HeaderChannelRegistry

JIRA: https://jira.spring.io/browse/INT-3545

Previously, the `DefaultHeaderChannelRegistry` was auto-started.
This caused the reaper to run and eventually start all the
`taskScheduler` threads, even if the registry was not being used.

- Defer the `start()` until the first channel is stored.
- Do not start the reaper if the bean has been explicitly stopped.
- Deprecate the implementation of `SmartLifecycle`.

Conflicts:
	spring-integration-core/src/main/java/org/springframework/integration/channel/DefaultHeaderChannelRegistry.java

Resolved.

__cherry-pick to 3.0.x__

Conflicts:
	spring-integration-core/src/test/java/org/springframework/integration/channel/registry/HeaderChannelRegistryTests.java