* Fix click target propagation with the Rasterize node
* Add the 'Write Attribute' node
* Remove tag_layer in favor of the new Write Attribute node, prune redundant attribute writes
* Replace the Vector<Upstream> type argument with the "editor:merged_layers" attribute
* Feature-gate serde derives behind cfg_attr in all runtime node graph type crates
* Refactor Table to move its hard-coded fields into an attributes field
* Encapsulate TableRow/TableRowRef/TableRowMut attribute fields behind accessor methods
* Remove TaggedValue::GraphicUnused
* Refactor Table<T> to use dynamic attributes instead fixed names
* Fix code review soundness concerns
* Add todo work
* Replace row-oriented Table<T> API with column-oriented access
* Fix attribute propagation bugs
---------
Keavon Chambers
Dennis Kobert
Timon