Enalbe sub-workflow to produce outcomes and outputs as you go, not necessary at the end

## Feature Request

### Problem Overview
At the moment, a sub-workflow is executed, and the result (output and outcome) can be set only at the end when you complete the workflow. Even the activity that allows you to set the outcome is intended for finalising the workflow.

### Proposed Solution
What if we were able to set outcomes and outputs in the middle of the workflow?
E.g.,
- Phase one completed, the phase1 outcome is set and the output for phase1 is set.
- The workflow is not completed yet.
- In the meantime, the parent workflow processes the path for phase1.
- Some more work is done, and phase2 is completed.
- The phase2 outcome is set and the output for phase2 is set.
- The main workflow starts processing the phase2.
- Eventually, the sub-worklfow is completed.

On top of that, we could also have more statuses except from (Finalized, Suspended...) like, file approved, file processed ... Those statuses would need to be mapped to one of the Elsa's standard status to ensure proper function of the engine, but the display would be more dynamic.

### Use Cases
For complex processes where multiple steps and states are involved. E.g., credit request (credit request initiated, credit request validated, credit request declined, credit approved).

### Impact of Feature
More extensibility.

### Priority
Just an idea, not a must.