Improve performance by span-tree removal

[farmaazon]

The span tree shall be replaced with AST + structure with data necessary for widgets

Tasks

Preview Give feedback

1. Malfunctioning edge after detaching source end #6772
   --bug -gui g-controller g-graph-editor p-high +5
   
2. Implement AST operations (removing, adding argument, replacing...) in place of SpanTree actions.
3. Create a data structure assiciating data from execution context with AST (so it will be easily used by the widgets)
4. Improve source code reference type in AST.
5. Generate Widgets from AST + data from controllers.
6. SImplify edges and nodes updates in Graph Editor (to not make unnecessary changes).

[farmaazon]

There's no span-tree in new GUI.