[Epic] Node Graph Refactor

[rprospero]

Focus

Based on recent discussion, we would like the following improvements on the Node Graph branch. This epic is likely to grow as this refactoring is refined.

Tasks

• The structure defining edges within the graph should label edge nodes by name and not by index
• We should use a proper Graphable concept for nodes that can be graphed (refactor: Establish Graphable Concept #2037)
• Start with generators connected by configuration
• Allow marking keywords as input and output
• Declare keywords as input versus output
• Spilt QML modules #2054
• Merge model events with main code
  ...