Introduce a "physical" container resource/controller differentiated from the current "logical" container type

We're starting to reach a point where more than one controller needs to manage the state of a physical container. Making a lower level container type that can serve as a re-usable child resource of multiple parent controllers would allow us to centralize all our container lifetime logic in one controller and let other controllers focus purely on maintaining their unique business logic.

Start by reading the existing logical container type and the controllers that manage container state. Define the physical container's reusable child-resource boundary and centralize container lifetime logic without displacing each parent controller's unique business logic; completion requires agreement on that design and its implementation scope.

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