UpgradeActions: Explore / define how to determine the upgrade action needed for each item

[azriel91]

Enables development / collaboration / seamless execution by defining the data model, rules, and workflow.

Need to answer:

• How can the framework tell if a value is changed? (easy, PartialEq)
• How can the framework tell if a data type is modified? (medium, enum discriminant PartialEq?)
• How can the framework tell if a flow item is modified? (hard, store item version?)
• How can the framework tell if a flow item is added / removed? (medium, item ID? restrict developer from reusing ID with different type)
• How does the developer define their data types -- Params, State, StateDiff?
• How does the developer define flow versions?