The `SecurityContextPropagationChannelInterceptor` has been migrated to `spring-security-messaging`.
Since it was only the class in the `spring-integration-security`, it is now fully considered
as deprecated
* Remove all the tests from `spring-integration-security`
* Modify `HttpDslTests` to demonstrate the `spring-security-messaging` in action
which has been replaced with whatever there was in `spring-integration-security`
* Remove redundant `exclude group: 'org.springframework'` for security
dependencies in `build.gradle` since all of them rely on the same SF deps
as SI
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