* feat: Make Executor id field mandatory
When checkpointing is involved, it is critical to keep executor ids consistent between runs, even when recreating a new object tree for the workflow.
The default id-setting mechanism generated a guid for part of the id, making it not work when restoring from a checkpoint.
This change prevents this situation from arising.
* feat: Enable running untyped Workflows
With the change to enable delay-instantiation of executors and support for async Executor factory methods, we must instantiate the starting executor to know what are the valid input types for the workflow.
To avoid forcing instantiation every time, and to better support workflows with multiple input types, we enable support for build and interacting with the base Workflow type without type annotations, and remove the requirement to know a valid input type when initiating a run.
* feat: Support Output from any executor and multiple outputs.
* fix: FanIn Edge does not work
We were not creating the state for FanIn edge in EdgeMap correctly, leading to crashes. After fixing that, it turns out the logic in FanInEdgeRunner was only forwarding the last message, not all of them.
* fix: Remove duplicate code and fix typo