container set next steps: enhanced depends logic

MVP/v1.0 implementation only supports basic declarative `dependencies. This is limited compared to DAG templates:

* Cannot have partial dependencies - i.e. start whenever one of the dependencies have started
* Dependencies must exit 0 - i.e. what about starting just when the dependency is just complete, regardless of exit code?

See #2551

Start with #2551 and the current MVP/v1.0 container set next-steps implementation. Compare its basic declarative dependencies with the DAG-template behavior described here; done means agreeing on and implementing partial-start and completion-regardless-of-exit-code semantics.

Written by the indexing model from the issue text.