XD-1368 Refactor container to remove shared module context

Added a small bootstrap context that pre instantiates SharedContextInitializers, ApplicationListeners specifically for providing bean definitions (e.g., MessageBus) to the ContainerContext. The ContainerContext holds what it did before (Control channels, ModuleDeployer, Plugins) and is now also used to create shared channels and other resources created during module deployment. The intention is to simplify the XD container architecture and the ability for end users and XD developers to extend it.

This PR addresses https://jira.spring.io/browse/XD-1368 and https://jira.spring.io/browse/XD-1262 and is prerequisite to :
https://jira.spring.io/browse/XD-432
https://jira.spring.io/browse/XD-912
https://jira.spring.io/browse/XD-1342
https://jira.spring.io/browse/XD-1343
https://jira.spring.io/browse/XD-1348